62304-2RS Sealed Ball Bearing 17mm x 52mm x 21mm 62304-2RS Sealed Ball Bearing, Bearing inner diameter is 17mm, outer diameter is 52mm and the width is 21mm, Bearing is made of Chrome Steel, each bearing has 2 Blue Rubber Seals to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.