R2-2RS Sealed Ball Bearings, this is a popular size that could be used in many application that uses this size 1/8" x 5/8" x 5/32" inch. Bearings are made of Chrome Steel, each bearing is rubber sealed from both sides to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease, Bearings are packed 10 bearings in one plastic tube.