This is the Heatsink Head for the O.S. Max 55AX Engine, (OSMG0556). This part, also known as a cylinder head mounts to the top of the crankcase, holds the glow plug and has cooling fins to dissipate heat. FEATURES: Replaces damaged cylinder heads. One-piece aluminum construction with brass gasket insures tight fit with crankcase. INCLUDES: One Heatsink Head for the O.S. Max 55AX Engine One brass washer. REQUIRES: Screws #79871150 (OSMG8791) to mount cylinder head to crankcase. OS EnginesPart OSM25704000