Deploy your favorite stock (or brace) faster than ever. The Fastback Receiver Extension attaches to any firearm that accepts a Mil-Spec receiver extension (buffer tube). Once installed, this allows you to easily pull the stock (or brace) back to an extended position, without pressing a release button.Personal Position Preset. P3 offers multiple customizable lengths presets to ensure the stock or brace extends to your personal position every time it is deployed. Simply adjust the indexing screw into one of the holes to customize your preset.