This is a pistol grip that will fit the STEN MK2 or MK3 trigger housings. It is made in the USA and is a R922 compliant part. It is very heavy duty, has a slot for the sling loop, holes if you want to install wood grips, and brings your hand closer to the trigger for a more natural feel. The notch at the top is for installing a corresponding 3/16" pin in the trigger frame. This would prevent the installation of a standard shoulder stock.