AT3 Tactical AR-15 Pro Quad Rail Free Float Handguard Tungsten 15in. Thats what we offer with the AT3 Pro Quad Rail. It uses the same simple installation as our SPEAR M-LOK handguard has plenty of lightening for maximum comfort and it works with Mil-spec uppers as well as our Billet Upper to match the sleek contours. Specifications for AT3 Tactical AR-15 Pro Quad Rail Free Float Handguard: Manufacturer: AT3 Tactical Finish: Anodized Fabric/Material: 6061 Aircraft Aluminum Gun Make: AR Platform Gun Model: AR-15 Gun Type: Handgun Handguard Type: Free-Float Handguard Style: Quad Rail Gun Rail: Quad Rail Gas System Length: Rifle Length Inner Diameter: 1.35 in Mount Type: Rail Package Contents: AT3 Tactical AR-15 Pro Quad Rail Free Float Handguard AT3 Tactical AT3-QR-15-TG: AR-15 Pro Quad Rail Free Float Handguard Tungsten 15in