Cross armory's stock lock is designed to comply with fixed stock requirements in states with restrictions, such as ca and ny.It is intended for owners who want to go featureless, but don't want to buy a new stock.Stock lock can be attached at any point on the buffer tube, not just the pin holes (an advantage over many other fixed stock solutions), and allows your adjustable buttstock to be immovably attached on the buffer tube without permanently altering your weapon.It is machined from billet 7075-t6 aluminum with a black finish and includes two allen wrenches.This model is comaptible with ar-15 style firearms.Rails: BlackType: Stock AdaptorFirearm Type: Stock LockFirearm Model: AR15/M4Material: 7075 AluminumFinish: 7075 Aluminum