ATF approved! Adapter with Shockwave Blade Pistol Stabilizer for Master Piece Arms .45acp. It bolts to your gun and maintains a tight precision fit under rapid fire with the aid of a machined set screw, that bolts into the existing rear threaded hole. *This part number for the Adapter, pistol buffer tube and Shockwave Blade, other parts sold separately. weighs about 12 ounces**TELL US IN THE COMMENTS SECTION OF YOUR ORDER IF YOU HAVE AN OPEN BOLT MAC-10, WE NEED TO GIVE YOU A DIFFERENT BOLT AND INNER THREADED BLOCK.