Spacers sit between the two bearings inside a wheel. Speed rings sit between the bearing and the truck hardware. Together they can help keep the assembly aligned when the axle nut is tightened.
Use the correct size
Choose hardware made for standard skateboard axles and wheels. Missing or mismatched parts can create unwanted play, drag or alignment problems.
Tighten with care
Tighten the axle nut firmly, then check that the wheel spins freely and does not shift excessively.