SFR188-2RS Flanged Stainless Steel Sealed Ball Bearing 1/4" x 1/2" x 3/16" inch One Ball Bearing SFR188-2RS Flanged Sealed Stainless Steel Ball Bearing, Bearing inner diameter is 1/4" inch, Bearing outer diameter is 1/2" inch and Bearing width is 3/16" inch, each bearing are rubber sealed from both sides to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease.