If your firearm doesn't already have a 1913 attachment rail on the rear choose the appropriate adapter. 8-inch Armbar, Brace Adapter, JMac 1913 Folding Mech - not assembled Lightweight and Rigid Modular Design - Brace/Stock with many mounting options Integrated QD Sling Socket 8"" Length 7075 T6 Aluminum Hard-Coat Anodized. This adapter mounts to the end of our AB (Arm Bar) and allows you to install braces like the TailHook from Gear Head Works. Anti-Rotational design 7075 T6 Aluminum Type 3 Hard-coat Anodize. Includes: Arm Bar-Brace Adatper Socket Head Screw Arm Bar-Brace Adapter Anti-Rotation Pin Mfg: Jmac Customs