Continuous Top Picatinny Rail, (sides and bottom are designed to accept picatinny rails) Weight: .8 lbs ID of Forearm: 1.35 inches Barrel Nut Thread: 1 ¼"-18 9" Free Float Hand Guard Magpul M-LOK attachment System T6 Aluminum Ultra Lightweight Handguard slides over Barrel Nut and Is Locked Against Receiver With Three Screws Hard Coat Anodized Finish