This wrench allows the shooter to put the exact amount of pressure needed on the barrel nut while attaching the barrel to the receiver. Constructed of high strength steel with 4 tightening fingers. This wrench has 2 sides with different hole patterns the original Armalite A2 barrel nut on one side and a 4 pin pattern for the current hole pattern. Notes:Does not fit: DPMS LR-308 (Use Product #294971), or AR-15 (Use Product #123930).