The Planet Eclipse Muffler Barrel Kit is designed to allow the occasional dry-firing (firing without paintball) of Eclipse markers. Most markers require some kind of "blow back" on the face of the bolt that comes from firing paintballs to prevent damage to the internal components. Dry firing is not advised for any marker. But the muffler barrel can help simulate firing a paintball and provide some blow back force on the bolt system. It also reduced the noise generated when dry firing significantly.