HPI servo horn slide carburetor. This servo horn set for use with slide valve carbureted engines. This set is used on the HPI Nitro 3, Nitro MT, and Super Nitro vehicles. HPI servo horn slide carburetor is constructed of black plastic. INCLUDES: One long arm servo saver. One short arm servo saver. Four plastic servo mounts. Required Parts Assembly on vehicle. Appropriate slide valve linkages.