ABEC scale - WikipediaThe ABEC scale is an industry accepted standard for the tolerances of a ball bearing.  Due to these factors, an ABEC 7 classified bearing could perform better than an ABEC 3 bearing. Bearings not conforming to at least ABEC 1 cannot be Abec vs. Skate Rated™ - Support - Bones BearingsIn an application like this, an ABEC - 7 or 9 bearing rating may be appropriate. However, a skateboard with 54mm wheels turning 20,000 RPM will be traveling 
What an ABEC Rating Tells You About Skateboard BearingsJul 22, 2018 - Skateboard bearings often have an ABEC rating that indicates the level  ABEC 7 bearings would be very fast and smooth, but very expensiveLUCKY ABEC-7 Bearings : Skateboard  I wish I had more closely inspected these bearings before skating with them. As you can see in the photo, one of the four bearings was not produced properlyWhat Are ABEC Ratings? | AST BearingsIt was developed by the Annular Bearing Engineering Committee (ABEC) of  There are five classes, going from widest tolerances to tightest: 1, 3, 5, 7, and 9