BCM MK2 Receiver Extension for your AR15, M16, M4. Machined from 7075T6 and manufactured to Mil-Spec dimensions and specifications. Mil-Spec receiver extensions have a slightly smaller dimension where the stock slides on. *NOTE* These buffer tubes require a rifle action spring and specific BCM MK2 buffer, carbine and rifle buffers will NOT work. RSR - TTTR70-SDB-33-TNC
