Soooo, apparently the M100 and M416 have different wheel bearings, grease seals and races. They do both share the same nut size of 2 & 1/16". The wheel bearings for a M100 are part number Timken 18590, or NAPA 18590. The Race is 18520 & the Grease Seals are part number 21101. I happen to have an m100 axel and I learned all of this the hard way.