sentences:  Bearings are usually rated on the ABEC scale, a measure of the manufactured precision tolerance, ranging from 1 (worst) to 9 (best) in odd numbers.The ABEC standards were originally intended for high-speed machinery, not skating applications, and do not account for the quality of steel used, which is very important for how long bearings last.While higher rated bearings are generally better in overall quality, whether they automatically translate to more speed is questionable.