Wheels and bearings for skates, scooters and skateboards. Chose appropriate size and hardness of wheels. Tougher wheels are faster, but bump more. Softer wheels have better adhesion and are more comfortable on a coarse surface. The higher the number, the higher wheel hardness - 85A wheels are then harder than 80A. Choosing bearings is much more complicated. Norms ABEC and ILQ with number plate are two most common norm used for bearings. Bearings ABEC 9 are more accurate than ABEC 5, as well as ILQ 9 are better than ILQ 5. Used materials are also very important. The price of bearings reflects overall quality very well.