The MOE Stock Com-Spec model (Magpul Original Equipment) is a drop-in replacement buttstock for AR15/M16 carbines using Com-Spec sized receiver extension tubes. Designed for light, fast action the streamlined A-frame profile avoids snagging and shields the release latch to prevent accidental activation. The Com-Spec Model includes a standard 0.55 inch rubber butt-pad which provides positive shoulder purchase to prevent slippage even with body armor or modular gear.
Unsure whether Mil-Spec or Com-Spec is required? Link