This is the Stock replacement Piston and Cylinder for the OS Max 61FX. These parts are located in the body of the crankcase. FEATURES: ABN construction Non-ringed INCLUDES: One Piston One Sleeve REQUIRES: Assembly into engine. Line up notch on sleeve with notch on crankcase SPECS: Total cylinder sleeve length: 41.5mm (1.63") Bore: 24.0mm (0.95") Total ports: 5 COMMENTS: The piston and sleeve are only available as a pair. They cannot be purchased individually.OS EnginesPart OSM27753000