Now, to make your wheels spin you need bearings. Skateboard bearings come in just the one size. Bearings are classed by either ‘ABEC’ or ‘Skate Rated’.
With the ABEC rating, the higher the number the better the bearings will be, unfortunately this doesn’t really apply to skateboarding as these ratings are measured at 20,000 - 30,000 revolutions per minute to get their ratings.
Most bearing companies are moving away from the ABEC rating and using the ‘Skate Rated’ rating as these have been designed to be used purely for skateboarding.