S608-2RS Ball Bearing Sealed Bearings Stainless Steel Ceramic Balls Si3N4 S608-2RS Ceramic Bearing is low friction 8mm axle skate bearing, bearing is double sealed, radial and deep groove ball bearings, It works in skateboards, longboards, inline skates, rollerblades and roller hockey,bearing is closed with seals to protect the bearing from dust or any possible contamination.S608-2RS is made of Stainless Steel with Si3N4 Ceramic (Silicon Nitride) balls.