This is our only buffer spring that will function in DPMS Pattern .308 / 6.5 CM large frame carbines using a standard 7" deep M4 buffer tube and a 2.5" short buffer. It is also appropriate for use in SR-25 / Armalite Pattern intermediate depth carbine large frame carbines using 3.25" buffers. It is also appropriate for use in standard 7" deep M4 tubes with any over gassed carbine of any lesser caliber (5.56, 6.8 SPC, 6.5 Grendel, etc.)
