The rubber buffer stop is used for FM-15 upper BOLT braking cushioning.
If you are using the FM-15 upper with the SARB-15 kit, FOXTROT MIKES recommends adding a buffer pad for the BCG to prevent damage to the upper.
Although our shooting tests without the buffer pad showed no issues, we still recommend installing this buffer tube kit.
*The product will be shipped via airmail with tracking or ePacket service if ordered individually.