This arbor fits Hudy, OFNA, Integy, 3 Racing, etc tire truers that have an 8mm drive shaft. Fits front wheels for Losi & Associated Truck foams and front Custom Works & RC4LESS dirt oval foam tires and any wheel that uses a non-flanged 3/16 id front bearing. Since various types of wheels are different and each has their own bearing recess depth, we have included a 0.013" thick shim to give your arbor the ability to fit almost every type of front wheel. If your bearing doesn't recess all the way into the wheel then use the shim, if your bearing is deeply recesed you won't need the shim but keep it incase your wheels ever change.