The BCM AR-15/M16 Pistol Receiver Extension kit has a 1.2” outside diameter which makes it compatible with the Sig Sauer SB-15 Stabilizing Brace. Made from 7075 T6 aluminum with a hard coat anodized finish, the kit also includes a castle nut, carbine buffer, carbine action spring, and QD receiver end plate.
AR-15, Issue:11, Page:041
Big Book Catalog, Issue:72, Page:049
SPECS: Made in the USA and manufactured from high quality 7075 T6 aluminum.