R168ZZ Ball Bearings 1/4" x 3/8" x 1/8" 10 Bearings 10 R168ZZ 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, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease.