The above comment is correct about ABEC ratings on bearings.
Let me give you this from the perspective of an inline skater. Bearings used in Skate Wheels are measured by the ABEC standard from ABEC 1 to 9. For the average 150 lbs recreational skater ABEC 5 bearings are find, they roll smooth and easy. As this same skater progressed into Fitness skating they would want to move to abec 6 or 7 as the 5's would not roll well at the higher speeds, again the same skater competing in a race would want ABEC 9 or higher bearings to eliminate as much friction as possible (most pro skaters will not put oil in their bearings as this adds friction). |