If your firearm doesn't already have a 1913 attachment rail on the rear choose the appropriate adapter! Skeletonized Tube, 6 inches long and 6 positions with JMAC's 1913 folding mech - Not Assembled This M4 tube adapter replaces the standard buffer tube to ensure the stock folds as flat as possible! Fits most M4 style stocks/braces Lightweight and Rigid Integrated QD Sling Sockers 6" Length 6 positions Compatible with SIG folding mechanisms 7075 T6 Aluminum Type III Hardcoat Anodized JMAC 1913 Folding Mechanism Mfg: Jmac Customs