Designed for a precise and tight fit into the upper, Sons of Libertys M76 Handguard uses a proprietary wedge lock system. This system keeps the handguard tight against the barrel nut and upper receiver. Features a full length picatinny top rail, MLOK on the 3" 6" and 9 OClock positions, and a QD Socket. Black Hard Coat Anodized Finish to withstand the elements.Features :"15" Length,,Inside Diameter 1.3";"Hard Coat Anodized,Steel Barrel NutIncludes QD Socket