Please Read - Stepped Spacers are used when you have 6mm (smaller than the inner diameter of bearings) axles. These go in between the bearings, and sit on the bearings, which Precisely aligns wheel assembly for speed & true spin. Made with structural aircraft aluminum for high strength & durability. Dissipates heat buildup – radiator for your skates. Dampens vibration & noise – shock absorber for your skates. Fits standard 608 bearings with 6mm axles. Includes 8 spacers.