B5 Systems SRK Extension Kit, Black - SRK - 1660

The Sierra K Receiver Extension Kit is the proprietary mounting system for the Sierra K Buttstock. It consists of a reduced-length, mil-spec diameter, 7075 aluminum, 5-position receiver extension, a short heavy buffer (3.5 oz), extra power spring, castle nut, and quick disconnect end plate. All parts are made of mil-spec materials and finishes and proudly Made In The USA.