The HK Parts VP9 standoff is designed to keep the slide in battery to allow discharge when the firearm is pressed against or comes into contact with an object. It is an excellent self-defense addition. The standoff device slides effortlessly onto your pistol frame and locks into place with a Picatinny rail. Each unit is made 100% in the USA. No special barrel needed they work with stock OEM standard length. Made from 7075 T6 aluminum.