16004-2RS Sealed Ball Bearing 20mm x 42mm x8mm One Bearing 16004-2RS Sealed Ball Bearing, the inner diameter is 20mm, outer diameter is 42mm and the width is 8mm, 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.