Convert your 3/8 "hex" drive type magneto to the advantages of our MM74E model (see description). Kit includes a newer design bearing bronze top ring, and the lower 'no leak' drive base mount is crafted from one-piece stainless steel. Top hex drive coupler has an oilite thrust washer. Comes with instructions and all hardware needed. If you wish to keep the original 'alnico' type rotor, you will need to choose the "no rotor" option. If you want to update to our strong and permanent rare-earth rotor, choose "with rotor", saves money rather than buying it separately. To help decide, we advise you to check the 'hex hole in the bottom of rotor for wear, check the points-cam condition, and the magnetic area. Note: "with rotor" requires mag head dis-assembly. It may not pay to go this route if a lot of internal parts will also be needed. Contact us for more info in your particular case.