6203-2RS-12 Sealed Ball Bearing 3/4" inch x 40mm x 12mm 6203-2RS-12 Sealed Ball Bearings, the inner diameter is 3/4" inch, outer diameter is 40mm and the width is 12mm, Bearing is made of Chrome Steel, each bearing has 2 Rubber Seals to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.