If you are a serious skateboarder, it is important to buy good skateboard bearings. The first thing you will hear about skateboard bearings is the ABEC rating.
The ABEC rating is a system that measures the physical limits and tolerances of ball bearings in high-speed spinning machinery. ABEC ratings are 1, 3, 5, 7, and 9. 1-rated bearings are the lowest quality, and 9-rated bearings are the highest quality.