The AR/MCX Stock Adapter allows the user to mount a picatinny-style stock attachment (such as the SIG MPX folding stock or brace) in place of an AR15 style buffer tube. Many firearms utilize the buffer tube attachment of the AR15 in order to mount common stocks & braces, but do not mechanically require the tube for an in-line buffer spring. For these weapons, this product offers a modular alternative for attaching stocks or other accessories. The kit is composed of two parts and an attaching bolt. The externally-threaded adapter plug fits into the threaded buffer socket or ring. The adapter rail section firs into the slot in the adapter plug and the two are secured to each other and the firearm by a hex-socket bolt and lock washer. This product will not work with a standard AR 15 lower and the MCX upper and is intended only for applications where the carrier and buffer tube do not protrude past the receiver ring.