17287-2RS Bearing 17x28x7 Si3N4 Ceramic Sealed17287 2RS Sealed Ball Bearing with Si3N4 Ceramic Balls Silicon Nitride 17mm x 28mm x 7mm Made for bicycles 17287 2RS Sealed Ball Bearing with Si3N4 Ceramic Balls, bearing is made from Chrome Steel with Ceramic Balls (Si3N4),17287 2RS bearing is closed with rubber seals to protect the bearing from dust or any possible contamination,bearing is sealed and self lubricated,17287 2RS bearing is lubricated with grease. 17287 2RS Ball Bearing Deep Groove Ball