The Sight Systems XS AR Upper & Lower Receiver Armorers Block is designed to allow gunsmiths or do-it-yourself enthusiasts to hold an AR-15/M4, AR-10, SR-25 or DMPS GII receiver in a bench-mounted vise to assemble, modify or maintain almost every AR pattern modern sporting rifle available. Made in the USA from 6061 T6 aluminum, the versatile, durable, and reliable XS Armorers Block comes with pins to lock in the receiver and fitment screw for the AR 15 lower. To allow bracing into the mag well of AR10 lowers, XS offers a 3D printed adaptor plate for purchase. The Armors Block works with a DPMS patterned 308, DPMS GII, Armalite Rifle, and standard AR 15/10 pattern rifles.