Bowden Tactical J1355315C Cornerstone Competition Handgaurd 15" M-LOK With Competition Top, Hard Coat Black Anodized Aluminum, Pre-Heated 4140 Steel Barrel Nut For AR-Platform, Full Flat Top A 1.3 Inch I.D. Will Accommodate Most Low-Profile Gas blocks. Some Interference With Clamp-On Style Low Profile Gas blocks Is Possible. MLok slots at The 3, 6 And 9 Positions Are manufactured To Magpul standards. This ensures Proper fitment With Any Magpul Certified Accessories. Every AR10 & AR15 Cornerstone Handguard Comes With a Pre-Heat Treated, 2 Inch Length 4140 Steel Barrel Nut. This ensures Rigid, Rock-Solid Accessory Mounting. The Barrel Nut Has Been nitrided, Not phosphated. Mounting instructions And Hardware Are Included With Every AR10 & AR15 Handguard. Material: 6061-T6 Aluminum Finish: Anodized Rails: Picatinny Free Floating: Yes