The Mechtech Carbine Conversion Unit (CCU) is an ‘upper’ for an autoloading pistol. Accessory items can be added to the basic unit, such as sights, adjustable stocks and additional rail systems.
The CCU is not a firearm and requires no special licensing to purchase. Under federal law (BATFE) it is perfecty legal to install a pistol lower and then remove the lower and reassemble the pistol. The unit comes completely assembled and test fired.
The CCU is offered for many common pistol frames like Glock and the venerable 1911. It is also available in several calibers although the video above demonstrates the 10mm Glock CCU.