VXB Brand, 163110-2RS Sealed Ball Bearing 16mm x 31mm x 10mm One Bearing 163110-2RS Sealed Ball Bearing, Bearing inner diameter is 16mm, Bearing outer diameter is 31mm and Bearing width is 10mm, 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.