KNIGHT'S ARMAMENT 5.56MM NATO/7.62 BARREL EXTENSION WRENCH FOR SR-15/SR-25 The KAC Barrel Extension Action Wrench is used to securely hold an SR-15 or SR-25 upper receiver in a bench vise so that work may be performed on the muzzle device and/or rail system. It is inserted through the rear of the upper receiver to engage the barrel extension. This tool is compatible with SR-15 E3 and SR-25 Barrel Extensions ONLY. NOTE: This tool can be damaged by using it in a standard square lug bolt AR-15 barrel extension. Mfg: Nightforce