This is Proto48 100T Roller Bearing Truck kit. It is designed to accept 3/32ID x 3/16 OD flanged roler bearing. You can find sets of 10 from EBay and cost $20 and can be found by looking for "Slot car bearings." These are flush mount such as what comes with the American Models Railgon. These are designed for use with Protocraft 36" axles rated for 100Tons. This should be assembled with CA or Cypox and have interior springs and brake shoe detail.