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 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.