The Classic Army Full Teeth Piston is one of the latest parts available in the series of upgrade parts manufactured by CA airsoft. The piston body is lightweight so its easier on the gearbox and all of the teeth are metal. These features put this polycabonate piston in a different class from other pistons.
The use of aftermarket airsoft parts is not an exact science. Some parts may require fitting even thought they were designed to fit without modification. Professional installation of upgrade parts is highly recommended.