Description: Reduce friction inside the hub of the bearing by adding durable SPACERS and WASHERS. Make your bearings stress-less and prevent your bearings from exploding or seizing. Increase your wheel & speed and bearings & life by adding Professional Speed Kit. 608 bearing;Designed for skateboarding, long board, inline skate and electric skateboard. Includes 8 professional-grade bearings, 4 skateboard spacers (which fit between the bearings)and 8 Speed Washers (which fit on the outside of the bearings). Specification: Material: chrome steel Bearings Size: 21mm (outer diameter) x 7mm (width) x 8mm (inner diameter/axle) Package Includes: 8 x professional-grade bearings 4 x skateboard spacers(Random Color,Black or Silver) 8 x Speed Washers(Random Color,Black or Silver)