Product Description316 – Must have the P218G engine Serial numbers 420,001 to 999,000 & Serial numbers 10,001 to 120,000317 – Must have the replacement Onan P218G engine in the tractor No serial number range is affected, you must check your engine model. If you have the Kohler engine in your 317, this coil will not work.318 – Must have the P218G engine Serial numbers 420,001 to 999,000 & Serial numbers 10,001 to 120,000420 – Must have the P220G engine Serial numbers 420,001 and aboveNotice:Durable and easy to installBrand new and High quality replacement.