NGK Japan C7HSA Spark Plug. 10mm Thread. Much Better Than OEM Chinese Spark Plugs. Increase Fuel Mileage And Reliability With These Great Plugs! Common Size ON Most: 49cc-150cc Gy6 Scooters 49cc-125cc Pit Bike Engines. 49cc- 125cc ATV Engines. Many More, Too Many To List.