The ACE Hammer Stock is reported to be the world's strongest AR-15 stock by the manufacturer and that claim seems to be right on the money. Precision machined from heat treated aircraft aluminum, the ACE Hammer Stock is heavy duty without adding much weight. The assembly comes with a 7-position tube that is marked to take all the guess work out of adjustment. As an additional measure of safety, the adjustment lever can be locked in a single position, essentially making it a fixed stock. Heavy duty-meat tenderizer checkering at the toe of the stock makes the ACE Hammer an effective striking implement as well. Requires a carbine buffer and spring.