All of the bearings you can buy in a skate shop fit in all of the wheels you can buy in a skate shop - You need two bearings for each wheel.

A bearing has a large outer ring (-> fig. 01A) and a smaller inner ring (-> fig. 01C). In between the two rings are usually steel balls (-> fig. 01B), which set your wheels in motion. The shields seal the bearings and protect the interior and the balls from dirt and dust. The balls lie in a so-called ball-cage (-> fig. 01D) so that they stay in position at all times. Bearings are available in sealed versions (ZZ) or in half-sealed versions (Z), which have only one shield. Half-sealed bearings are more sensitive, but they are also faster. A set of bearings often comes with four spacers (-> fig. 03). These spacers are placed between the two bearings and onto the axle during assembly. They protect your bearings from being pushed in.

A set of bearings often comes with four spacers (-> fig. 03). These spacers are placed between the two bearings and onto the axle during assembly. They protect your bearings from being pushed in.

The ABEC-scale (ABEC 1 - ABEC 9) is the industry standard regarding the tolerances of ball bearings. It describes the precision of the bearings - the higher the ABEC number the smaller the tolerances of the bearings. That means that an ABEC 9 bearing is more precise than an ABEC 1 bearing. However, in skateboarding the ABEC-scale is often not that relevant. "Skate Tested Bearings" are manufactured specifically for skateboards and can better withstand the impact during hard landings as well as the pressure which amounts when turning. There are versions with six instead of seven steel balls inside available. The ultimate bearings are the Swiss Ceramic bearings, which have ceramic balls inside. Due to the extreme hardness of these ceramic balls, those kinds of bearings guarantee a very long working life.

If you take the time to clean your bearings every now and then, you increase the chance for a long and reliable working life. You can oil them using Bones Bearings Speed Cream (-> Fig. 02) or similar oil-based lubricants. If cleaning and oiling your bearings is too time-consuming for you, simply pay attention where you ride your board. Bearings should be kept away from dust as well as from rain, since they can and will rust.