Precision Machined with Maximum Strength Four Mil-spec Picatinny Rails with Free Float Extension for Versatile Accessory Applications Simple and Friendly Installation, no Gunsmith or Tool Required Solid Locking Features for Most Secure Fit Ultimate Tactical Solution to Enhance Accuracy under Toughest Environments Fits Carbine Length Model 4, 15, 16 and Variants Hard Anodized Finish for Wear Resistance UTG Rubber Rail Guards Included for Great Comfort and Protection