This cylinder and piston set from HPI Racing is for the HPI Nitro Star S-25 engine (used in Savage and other HPI trucks). Made of aluminum, brass, and chrome, this set will restore your engine to like-new performance without having to buy a new engine. Includes one piston and one cylinder wall sleeve that are direct replacement parts of those in the engine. Features four intake ports and one exhaust port. Part number: HPI 1439.