8 Si3N4 Ceramic Skateboard Bearings With Extended inner race No Need for Spacers Set of 8 Si3N4 Ceramic skateboard Bearings with extended inner race, that will eliminate the use of spacers, you will get more Stronger/smooth wheel set when you use these bearings, these bearings are sealed on one side (the outer side) with rubber seal,Bearings are made of Chrome Steel, these bearings have nylon cage to ensure the light weight and low friction, each bearing have One Rubber Seal to protect the bearing fromdust or any possible contamination.