Ballasted Ground Mount Solar Racking: The Complete Guide for 2025

Table of Contents

Key Insights

  • Ballasted systems excel in challenging terrain: Rocky soil, contaminated sites, and frozen ground conditions where traditional excavation is difficult or expensive make ballasted systems 3-5 times more cost-effective than conventional ground mounts.
  • Wind load limitations define geographic suitability: Most ballasted systems are limited to 120-150 mph wind speeds, requiring hybrid solutions or alternatives in hurricane zones and extreme wind areas, making proper site assessment critical for success.
  • Installation cost savings vary by application: While ballast materials add $0.10-0.20 per watt in costs, elimination of excavation and simplified installation can reduce labor costs by 15-25%, with greatest savings in challenging soil conditions.
  • Space requirements increase significantly: Ballasted systems typically require 15-25% more space than traditional ground mounts due to wider ballast footprints and increased row spacing, making them less suitable for space-constrained installations.

Ballasted ground mount solar racking systems represent a revolutionary approach to solar panel installation that eliminates the need for ground penetration while providing secure, stable mounting solutions. As the solar industry continues to evolve in 2025, these innovative systems are becoming increasingly popular for their versatility, cost-effectiveness, and minimal environmental impact.

What is Ballasted Ground Mount Solar Racking?

Ballasted ground mount solar racking is a mounting system that uses the weight of ballast materials—such as concrete blocks, gravel, or sand—rather than ground anchors or penetrations to secure solar panels in place. Unlike traditional ground mount solar systems that require driving piles or pouring concrete footings deep into the earth, ballasted systems rely on carefully calculated weight distribution to resist wind uplift and maintain structural stability.

The core principle behind ballasted solar racking is simple yet effective: by adding sufficient weight to the mounting structure, the system can withstand environmental forces without the need for invasive ground anchoring. This approach makes ballasted systems ideal for situations where ground penetration is difficult, prohibited, or undesirable.

Key Differences from Traditional Ground Mounts

Traditional ground mount systems typically require:

  • Excavation and ground penetration
  • Concrete footings or driven piles
  • Heavy machinery for installation
  • Extensive site preparation
  • Permanent ground modification

In contrast, ballasted systems offer:

  • Surface-level installation with no ground penetration
  • Portable and relocatable design
  • Simplified installation process
  • Minimal site preparation requirements
  • Reversible environmental impact

How Ballasted Solar Racking Systems Work

The engineering behind ballasted ground mount solar racking systems is based on fundamental physics principles. The system must generate enough downward force through ballast weight to counteract wind uplift forces, seismic loads, and other environmental stresses that could destabilize the solar array.

Physics of Ballast Weight vs. Ground Penetration

Wind creates both downward pressure and uplift forces on solar panels. The angled surface of solar panels acts like an airfoil, generating significant uplift forces during high wind events. Traditional systems transfer these forces directly into the ground through deep foundations. Ballasted systems, however, must rely entirely on gravitational force to resist uplift.

The basic calculation for ballast requirements follows this principle:

Required Ballast Weight = (Wind Uplift Force + Safety Factor) ÷ Ballast Effectiveness Factor

Wind uplift forces are calculated based on local wind speeds, panel dimensions, tilt angles, and height above ground. Safety factors typically range from 1.5 to 2.0, depending on local building codes and engineering requirements.

System Components Breakdown

Structural Frame: The foundation of any ballasted system is a robust structural frame, typically made from aluminum or galvanized steel. This frame distributes loads evenly across the ballast material and provides mounting points for solar panels.

Ballast Materials: Various materials can serve as ballast, each with specific advantages:

  • Pre-cast concrete blocks: Provide consistent weight and professional appearance
  • Poured concrete: Offers maximum density and custom shaping capabilities
  • Gravel or crushed stone: Cost-effective and easily adjustable
  • Sand: Provides excellent conformity to frame shapes

Mounting Hardware: Specialized clamps, rails, and fasteners secure solar panels to the ballasted frame while allowing for thermal expansion and maintenance access.

Types of Ballasted Ground Mount Systems

The ballasted solar racking market offers several distinct system types, each optimized for specific applications and installation requirements.

Pre-cast Concrete Ballast Systems

Pre-cast concrete systems use factory-manufactured concrete blocks designed specifically for solar applications. These blocks typically weigh between 1,500 and 3,000 pounds each and feature integrated mounting points for racking components.

Advantages:

  • Consistent weight and dimensions
  • Professional appearance
  • Integrated mounting features
  • Long-term durability

Disadvantages:

  • Higher transportation costs
  • Limited flexibility in ballast distribution
  • Requires crane for installation

Cast-in-Place Concrete Solutions

Cast-in-place systems use portable forms that are filled with concrete on-site. Companies like GameChange Solar offer innovative “Pour-in-Place” systems that combine the benefits of concrete ballast with on-site flexibility.

Key Features:

  • Reduced transportation costs
  • Custom ballast shapes
  • Optimal weight distribution
  • Professional finished appearance

Aggregate-Filled Ballast Systems

These systems use containers or frames that are filled with loose aggregate materials like gravel, crushed stone, or sand. The PowerRack system exemplifies this approach, using high-density polyethylene (HDPE) containers that weigh 15 pounds empty and can hold up to 550 pounds of ballast material.

Benefits:

  • Lowest transportation costs
  • Easy ballast adjustment
  • Local material sourcing
  • Simple installation process

Hybrid Ballasted Systems

Hybrid systems combine ballast weight with minimal ground penetration, such as shallow footings or ground screws. These systems offer enhanced stability while maintaining most benefits of pure ballasted designs.

System Type Weight per Unit Installation Time Cost Range Best Applications
Pre-cast Concrete 1,500-3,000 lbs Medium $$$$ Permanent installations
Cast-in-Place Variable Medium-High $$$ Large commercial projects
Aggregate-Filled 200-600 lbs Low $$ Residential, temporary
Hybrid Variable Medium $$$ High-wind areas

Advantages of Ballasted Solar Racking

Ballasted ground mount solar racking systems offer numerous advantages that make them attractive for specific applications and site conditions.

No Ground Penetration Required

The most significant advantage of ballasted systems is their ability to provide secure mounting without any ground penetration. This feature is invaluable in situations where:

  • Underground utilities prevent excavation
  • Environmental regulations prohibit ground disturbance
  • Rocky or frozen ground makes penetration difficult or expensive
  • Contaminated soil requires special handling procedures

Faster Installation Times

Ballasted systems can reduce installation time compared to traditional ground mount systems. The elimination of excavation, concrete curing time, and complex foundation work can significantly reduce project timelines. Installation time savings vary by project complexity and site conditions.

Lower Labor and Equipment Costs

Installation cost savings come from multiple factors:

  • No need for excavation equipment
  • Reduced skilled labor requirements
  • Elimination of concrete work
  • Simplified permitting process
  • Reduced site preparation needs

Labor typically accounts for 15-25% of total solar installation costs, and ballasted systems can reduce these costs in appropriate applications.

Suitable for Challenging Terrain

Ballasted systems excel in challenging installation environments:

Rocky Terrain: No need to blast through rock or use specialized drilling equipment.

Contaminated Sites: Minimal soil disturbance reduces contamination exposure and remediation costs.

Frozen Ground: Installation possible year-round without waiting for ground thaw.

Sensitive Ecosystems: Minimal environmental impact preserves natural habitats.

Portable and Relocatable Systems

Unlike permanent ground mount systems, ballasted installations can be relocated if needed. This flexibility is valuable for:

  • Temporary installations
  • Lease agreements with relocation clauses
  • Changing site conditions
  • System expansion or reconfiguration

Disadvantages and Limitations

While ballasted systems offer significant advantages, they also have important limitations that must be considered during system design and site selection.

Wind Load Limitations and Geographic Restrictions

Ballasted systems have inherent wind speed limitations based on the practical limits of ballast weight. Most systems are limited to wind speeds of 120-150 mph, making them unsuitable for extreme wind zones or hurricane-prone areas without additional engineering measures.

Geographic Limitations:

  • Hurricane zones may require hybrid systems
  • Tornado alley installations need special consideration
  • Coastal areas with salt spray exposure
  • High-altitude locations with extreme weather

Higher Ballast Material Costs

While installation labor costs are lower, ballast materials represent a significant expense. Concrete blocks can cost $50-100 per ton, while aggregate materials range from $20-40 per ton. A typical residential installation may require 10-20 tons of ballast material.

Increased Space Requirements

Ballasted systems typically require 15-25% more space than traditional ground mounts due to:

  • Wider ballast footprints
  • Increased row spacing for stability
  • Access requirements for maintenance
  • Safety clearances around heavy ballast

Snow Load Challenges

In northern climates, snow accumulation can create additional challenges:

  • Increased structural loads beyond design limits
  • Reduced panel clearance from ground
  • Difficult access for snow removal
  • Potential for ice damming issues

Ideal Applications and Use Cases

Understanding when ballasted systems are optimal helps ensure successful project outcomes and cost-effective installations.

Landfills and Brownfield Sites

Landfills represent one of the most successful applications for ballasted solar systems. These sites often have restrictions on ground penetration due to environmental concerns, making ballasted systems the preferred choice.

Case Study: 485 KW Delaware Installation

Solar Electric Supply designed and installed a 485 KW ballasted system for a military facility in Delaware. The project faced unique challenges including proximity to ocean salt spray and coastal installation requirements. The self-ballasted system demonstrated the durability of properly engineered ballasted installations in challenging coastal environments.

Key Project Requirements:

  • Coastal environmental considerations
  • 120 mph wind resistance
  • Seismic load compliance
  • Specialized drainage design
  • Lightning protection systems

Rocky or Hard-Packed Soil Conditions

Sites with rocky terrain, caliche, or extremely hard-packed soil benefit significantly from ballasted systems. Traditional excavation in these conditions can cost 3-5 times more than standard installations, making ballasted systems highly cost-effective.

Temporary or Lease-End Removable Installations

Agricultural lease agreements often require complete system removal at lease end. Ballasted systems can be completely removed without permanent ground modification, making them ideal for:

  • Agricultural land preservation
  • Temporary power needs
  • Demonstration installations
  • Mobile or relocatable systems

Environmentally Sensitive Areas

Ballasted systems minimize environmental impact in sensitive ecosystems:

  • Wetland buffer zones
  • Protected habitat areas
  • Archaeological sites
  • Scenic preservation areas

Engineering and Design Considerations

Proper engineering is critical for ballasted system success. Professional structural engineering ensures adequate ballast weight while maintaining cost-effectiveness.

Wind Load Calculations and Requirements

Wind load analysis follows ASCE 7 standards with specific considerations for ballasted systems:

Basic Wind Speed: Determined by geographic location and local building codes.

Exposure Category: Based on surrounding terrain roughness.

Importance Factor: Typically 1.0 for solar installations.

Panel Characteristics: Size, tilt angle, and height above ground affect wind loads.

Ballast Weight Calculations by Geographic Region

Ballast requirements vary significantly by location:

Wind Zone Basic Wind Speed Typical Ballast (lbs/sq ft) Example Locations
Low 90-110 mph 15-25 Interior Southwest
Moderate 110-130 mph 25-40 Most of Continental US
High 130-150 mph 40-60 Coastal areas, Great Plains
Extreme 150+ mph 60+ or hybrid system Hurricane zones

Structural Engineering Requirements

Professional structural engineering is essential for ballasted systems. Key design elements include:

Load Path Analysis: Ensuring forces transfer properly from panels through racking to ballast.

Foundation Bearing: Verifying soil can support concentrated ballast loads.

Stability Analysis: Preventing overturning under combined wind and seismic loads.

Fatigue Considerations: Ensuring long-term durability under cyclic loading.

Installation Process and Best Practices

Successful ballasted system installation requires careful attention to site preparation, component placement, and quality control procedures.

Site Preparation Requirements

Site Survey: Detailed topographic survey identifies drainage patterns and slope variations.

Soil Analysis: Geotechnical investigation determines bearing capacity and drainage characteristics.

Grading: Site should be graded to maximum 10% slope for stability.

Drainage: Proper drainage prevents water accumulation under ballast.

Step-by-Step Installation Guide

Step 1: Layout and Marking

  • Mark ballast positions using surveyed coordinates
  • Verify row spacing and panel clearances
  • Check for underground utilities

Step 2: Ballast Placement

  • Position ballast containers or forms
  • Ensure level placement within tolerance
  • Verify proper spacing and alignment

Step 3: Ballast Loading

  • Add ballast material to calculated weight
  • Distribute weight evenly within containers
  • Compact aggregate materials as needed

Step 4: Racking Installation

  • Mount racking components to ballast
  • Verify proper tilt angles and orientation
  • Check structural connections and torque specifications

Step 5: Panel Installation

  • Install panels according to manufacturer specifications
  • Maintain proper spacing for thermal expansion
  • Complete grounding and bonding connections

Quality Control Checkpoints

Critical quality control points include:

  • Ballast weight verification at 10% of locations
  • Structural connection torque checks
  • Grounding continuity testing
  • Final system alignment verification

Cost Analysis and ROI Considerations

Understanding the total cost of ownership helps determine when ballasted systems provide the best value.

Upfront Costs vs. Traditional Ground Mounts

Ballasted System Costs:

  • Racking hardware: $0.15-0.25 per watt
  • Ballast materials: $0.10-0.20 per watt
  • Installation labor: $0.05-0.15 per watt
  • Engineering: $0.02-0.05 per watt

Traditional Ground Mount Costs:

  • Racking hardware: $0.12-0.20 per watt
  • Foundation materials: $0.08-0.15 per watt
  • Excavation/installation: $0.15-0.30 per watt
  • Engineering: $0.02-0.05 per watt

Labor Cost Savings Analysis

Labor savings represent a potential economic advantage of ballasted systems in appropriate applications:

  • Elimination of excavation work: potential savings
  • Reduced skilled labor requirements: potential savings
  • Simplified installation process: potential time savings
  • Simplified permitting: potential cost reduction

Long-term Maintenance Costs

Ballasted systems typically have lower long-term maintenance costs:

  • No foundation settling issues
  • Easy access for panel cleaning
  • Simple component replacement
  • Reduced corrosion in non-penetrating systems

Leading Manufacturers and Product Comparison

The ballasted solar racking market includes several established manufacturers with proven track records and innovative solutions.

PowerRack System Detailed Review

The PowerRack system represents one of the most popular aggregate-filled ballasted solutions in the market.

Key Specifications:

  • Material: UV-stabilized HDPE
  • Weight: 15 lbs empty, up to 550 lbs filled
  • Dimensions: 37″ x 26″ x 26″
  • Tilt angle: Fixed 25°
  • Wind rating: 120 mph
  • Warranty: 25 years

Advantages:

  • Tool-free assembly
  • Stackable for efficient shipping
  • Compatible with standard 60-cell panels
  • Local ballast material sourcing

Corigy Ballasted Mounts Analysis

Corigy offers versatile ballasted mounting solutions with both portrait and landscape panel orientations.

Features:

  • 18° tilt angle optimized for most US locations
  • 5 cubic feet ballast capacity
  • UV-stabilized HDPE construction
  • Supports panels up to 60″ in portrait mode
  • 39.5″ panels compatible in landscape mode

GameChange Solar Pour-in-Place

GameChange Solar’s Pour-in-Place system combines the benefits of concrete ballast with on-site flexibility.

System Benefits:

  • Potential cost reduction compared to traditional systems
  • No risk of pile refusal
  • Minimal impact on site drainage
  • Industry’s longest spans and lowest post counts
  • Integrated grounding and wire management

FLEXRACK Series B Systems

FLEXRACK’s Series B ballasted systems target commercial and utility-scale installations with engineered concrete solutions.

Key Features:

  • UL 2703 compliant design
  • In-house structural engineering team
  • Pre-cast or cast-in-place options
  • 100% hot-dipped galvanized construction
  • 20-year mechanical warranty

IntegraRack BallastRack Solutions

IntegraRack offers multiple ballasted solutions including the IR-30, IR-15, and adjustable seasonal angle systems.

Product Range:

  • IR-30: Standard ballasted mount for single panels
  • IR-15: Low-profile design for weight-sensitive applications
  • IR-45ASA: Adjustable seasonal angle for optimized production
  • EarthBallast: Hybrid system with minimal penetration
Manufacturer System Type Price Range Wind Rating Warranty Best Application
PowerRack Aggregate-filled $75-100 120 mph 25 years Residential/Small commercial
Corigy Aggregate-filled $60-80 110 mph 20 years DIY installations
GameChange Pour-in-place $150-250 150+ mph 20 years Utility-scale
FLEXRACK Pre-cast concrete $200-300 150+ mph 20 years Commercial/Industrial
IntegraRack Multiple options $90-190 120-140 mph 15-20 years Versatile applications

Alternatives to Ballasted Systems

Understanding alternatives helps determine when ballasted systems are truly optimal versus other mounting approaches.

Traditional Driven Pile Systems

Driven pile systems use steel posts hammered or screwed into the ground to depths of 6-10 feet.

Advantages:

  • Lower material costs
  • Suitable for high wind areas
  • Minimal space requirements
  • Proven long-term performance

Disadvantages:

  • Requires ground penetration
  • Difficult in rocky soil
  • Higher installation labor
  • Permanent ground modification

Helical Pier Foundations

Helical piers use screw-like foundations that are rotated into the ground, providing excellent holding power in various soil conditions.

Best Applications:

  • Soft or sandy soils
  • High wind areas
  • Areas with poor bearing capacity
  • Seismically active regions

Concrete Footing Systems

Traditional concrete footings provide maximum stability but require significant excavation and concrete work.

When to Choose:

  • Extreme wind conditions
  • Large commercial installations
  • Long-term permanent installations
  • High seismic zones

Earth Anchor Alternatives

Companies like Nuance Energy offer innovative earth anchor systems that provide ballasted-like benefits with minimal ground penetration.

Osprey PowerRACK Features:

  • Handheld tool installation
  • No concrete required
  • Patented earth anchor technology
  • Rapid deployment capability
  • Pull-test verified stability

Regulatory and Code Compliance

Navigating building codes and permitting requirements is crucial for successful ballasted system installations.

Building Code Requirements by Region

Building codes vary significantly by jurisdiction, but common requirements include:

International Building Code (IBC): Provides baseline structural requirements for ballasted systems.

ASCE 7: Defines wind and seismic load calculations.

Local Amendments: Many jurisdictions modify standard codes based on local conditions.

Permitting Process Considerations

Ballasted systems often simplify permitting due to:

  • No foundation excavation permits required
  • Reduced environmental impact assessments
  • Simplified structural calculations
  • Faster plan review processes

UL Certification Requirements

UL 2703 certification is essential for ballasted systems, covering:

  • Structural integrity testing
  • Wind uplift resistance
  • Grounding and bonding compliance
  • Fire safety requirements

Future Trends and Innovations

The ballasted solar racking industry continues to evolve with new technologies and approaches emerging in 2025.

Emerging Ballast Technologies

Smart Ballast Systems: Integration of sensors to monitor ballast weight and system stability in real-time.

Modular Ballast Designs: Standardized ballast modules that can be combined for various system sizes.

Recycled Materials: Use of recycled concrete and other sustainable ballast materials.

Integration with Energy Storage Systems

Ballasted systems are increasingly being designed to accommodate battery storage systems:

  • Integrated battery enclosures within ballast structures
  • Coordinated grounding and electrical systems
  • Optimized layouts for maintenance access

Smart Monitoring and Maintenance

Advanced monitoring systems provide real-time data on:

  • System stability and ballast integrity
  • Panel performance and cleaning needs
  • Environmental conditions and loads
  • Predictive maintenance scheduling

Conclusion and Decision Framework

Ballasted ground mount solar racking systems offer compelling advantages for specific applications and site conditions. Success depends on careful evaluation of project requirements, proper engineering analysis, and selection of appropriate system components.

Key Decision Criteria Summary

Choose Ballasted Systems When:

  • Ground penetration is difficult or prohibited
  • Installation speed is critical
  • Site conditions favor surface mounting
  • System portability is desired
  • Environmental impact must be minimized

Consider Alternatives When:

  • Wind speeds exceed 150 mph regularly
  • Space is severely constrained
  • Ballast costs exceed alternatives
  • Local codes prohibit ballasted systems
  • Long-term permanence is required

Next Steps for Project Planning

Successful ballasted system implementation requires:

  1. Professional site assessment including geotechnical analysis
  2. Structural engineering review by qualified professionals
  3. Manufacturer selection based on project requirements
  4. Permit application with proper documentation
  5. Installation by experienced contractors familiar with ballasted systems

As the solar industry continues to mature in 2025, ballasted ground mount solar racking systems represent a proven, cost-effective solution for challenging installation environments. With proper planning, engineering, and execution, these systems can provide decades of reliable solar energy production while minimizing environmental impact and installation costs.

For projects considering ballasted systems, consultation with experienced solar professionals and structural engineers ensures optimal system design and compliance with all applicable codes and standards. The investment in proper planning and engineering pays dividends in system performance, longevity, and peace of mind.

Frequently Asked Questions

What is the maximum wind speed that ballasted solar racking systems can handle?

Most ballasted solar racking systems are designed to withstand wind speeds of 120-150 mph. Systems exceeding these limits typically require hybrid designs with minimal ground penetration or alternative mounting solutions. Geographic areas with regular wind speeds above 150 mph, such as hurricane zones, may need traditional ground mount systems or specially engineered ballasted solutions with additional safety factors.

How much ballast weight is typically required per solar panel?

Ballast weight requirements vary by wind zone and range from 15-25 lbs per square foot in low wind areas to 40-60 lbs per square foot in high wind zones. For a typical 400-watt solar panel (approximately 22 square feet), this translates to 330-1,320 pounds of ballast material depending on local wind conditions and safety factors required by building codes.

Can ballasted solar systems be relocated or removed completely?

Yes, ballasted solar systems are designed to be relocatable and completely removable without permanent ground modification. This makes them ideal for agricultural lease agreements, temporary installations, or situations where future site restoration is required. The ballast materials can be removed and the site returned to its original condition, unlike traditional ground mount systems that leave permanent foundations.

What are the main cost differences between ballasted and traditional ground mount systems?

Ballasted systems typically cost $0.32-0.65 per watt total, while traditional ground mounts range from $0.37-0.70 per watt. While ballast materials add $0.10-0.20 per watt in costs, savings come from reduced excavation, simplified installation, and lower labor requirements. The cost advantage is greatest in challenging soil conditions where traditional excavation costs can be 3-5 times higher than normal.

Citations

  • Solar module racking market size of $5.2 billion in 2024, expected to reach $12.8 billion by 2033 with 10.5% CAGR confirmed by Verified Market Report, 2025
  • PowerRack specifications: 15 lbs empty weight, up to 550 lbs filled capacity confirmed by GoGreenSolar and Current Connected product specifications, 2024-2025
  • Delaware 485 KW ballasted solar installation case study confirmed by Solar Electric Supply project documentation, 2025
  • Hurricane Sandy ballasted system survival confirmed by Solar Power World and Sunnova reports on ballasted system performance during major storms, 2012-2024
  • Average solar cost-per-watt of $2.56/W before incentives confirmed by EnergySage Marketplace data, 2025
  • Labor costs representing 15-25% of total solar installation costs confirmed by A1 SolarStore and This Old House market analysis, 2025

Take the Next Step with SolarTech Energy Systems

Ready to explore how ballasted ground mount solar systems could work for your property? With over 22 years of experience and 13,000+ successful installations across California, Arizona, Nevada, and Colorado, SolarTech Energy Systems has the expertise to determine if ballasted solar racking is the right solution for your unique site conditions. Whether you’re dealing with rocky terrain, environmental restrictions, or simply want a cost-effective solar installation, our in-house certified professionals will conduct a thorough site assessment and provide transparent pricing with multiple financing options. Don’t let challenging ground conditions prevent you from achieving energy independence and reducing your monthly electricity costs. Visit SolarTech Energy Systems today to schedule your free consultation and discover how our proven solar solutions can start saving you money while increasing your property value.

Related Articles

What is Passive Solar Heating? The Complete Guide to Natural Solar Home Heating

Oil vs Electric Heat: Complete 2025 Comparison Guide

Complete DIY Solar Panel System Guide 2025: Design, Install & Save $20,000+

SolarTech

"" indicates required fields

Step 1 of 7

California home with SolarTech panels
★★★★★ 2025 Top Solar Installer

Get Best-in-Class Solar
and Maximum Savings
with $0 Down

Join thousands of homeowners and start saving with our award-winning solar. Begin now with a free savings estimate.

  • ⚡ Personal savings estimate in <60 sec
  • 🎯 Instant 30 % Federal Tax Credit eligibility check
  • 📈 Projected boost to your home’s value

SolarTech has already helped 13 000 + homeowners cut energy bills with fast, no-pressure service.

This field is hidden when viewing the form

Claim up to $1,500 back when you go solar with SolarTech!

Complete the form to schedule your free consultation and take advantage of our limited-time Summer Savings offer.