Proline makes them... Works with 2 of their rims I believe. The Velocity and some other rim. I hear it's like $50 for all four and that's just the spinners... You'll still have to buy the other "Velocity" rims, unless you already have them.. Don't quote me though. I have yet to see them at my local hobby store and we have like 6 here. Good luck in finding them and if you do get them, post a pic....