All Bones Bearings are Skate Rated™ to withstand the destructive forces created by high performance skating. This is our way of saying that just using a bearing with an ABEC rating is not enough to ensure that a bearing will perform well for skating, since ABEC ratings were intended for electric motor bearings, not skate bearings. We have adjusted the tolerances, clearances, lubricant, and component materials to optimize Bones Bearings for use in dirty, high impact environments… where you skate. That’s why they roll faster and last longer than mere ABEC rated bearings. FEATURES: Accelerate faster. Roll farther and faster. Resist dirt and moisture better. Outlast the races, allowing them to be reused in most cases. Pre-lubricated with Speed Cream® racing lubricant. Single non-contact removable rubber shield for easy cleaning & less friction. High speed Nylon® ball retainer. Non-contact removable rubber shield. Skate Rated® clearances, tolerances, materials and lubricant provide the best performance and durability possible.