This is the right component if you want the feel and comfort of an adjustable or fixed AR stock. It bolts to your gun and maintains a tight precision fit under rapid fire. The addition of the AR stock will greatly improve accuracy and shot grouping as it provides a firm shoulder rest and helps to balance the weapon. This part number is for the adapter for the Mac-10 Semi Auto Open Bolt only. You will need an AR rear stock to complete the setup. See other parts numbers for complete set up. (gun and other accessories sold separately) Installation instructions & allen wrench included. * NFA rules apply, Addition of this item may require additional paperwork to be filed with the ATF, check with your local dealers.