R1238ZZ Shielded Ball Bearings, the inner diameter is 3/8", outer diameter is 3/4" and the width is 0.196", this is a popular size that could be used in many applications, Bearings are made of Chrome Steel each bearing has 2 metal shields 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.