Convert your stock early magneto or "hex" type to the advantages of our MM3 style (see MM3 description). Comes with instructions and needed hardware kit, not shown. If you have the stock 'long shaft' type rotor, you will need to choose the "with rotor" option. If you already have a 3/8 hex drive magneto head instead of a stock XLCH and do not want the updated rare-earth rotor, choose "no rotor". Note: "with rotor" requires mag dis-assembly and experience. With any other internal parts etc. that are needed, it may not be the cost-effective route to go, depending on your current magneto's condition.