The  hottest class in dirt oval racing is 1/8 Scale Late Model. The OFNA GTP is the car of choice and these arbors are just for them. The 17mm hex fits RC4LESS, OFNA and other 1/8 wheel. You get the arbor and tightening nut. For  use with a MAX MOD or COBRA tire truer only. Will not work on HUDY, INTEGY, ect truers.