Magpul MAG529-BLK: Replacing the standard AR15/M4 carbine stock receiver end plate, the Asap QD provides a tactical advantage by minimizing sling snagging and facilitating easy transition to and from weapon and reaction side shoulders. It accepts any push-button QD sling swivel as well as the Magpul QDM, and works with both mil-spec and commercial-spec carbine receiver extensions (buffer tubes). NOTE: The Asap QD is NOT compatible with A1/A2 fixed stocks as well as any other similarly mounted stock such as the Magpul PRS, UBR, and MOE Rifle Stocks.