FR168ZZ Flanged Shielded Ball Bearings, the inner diameter is 1/4", outer diameter is 3/8" and the width is 1/8", this is a popular size that could be used in many applications, Bearings are made of Chrome Steel, each bearing has 2 Metal Sheild 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.