FR2-5ZZ Flanged Ball Bearing 1/8" x 5/16" x 9/64" inch FR2-5ZZ Flanged Shielded Ball Bearing, the inner diameter is 1/8" inch, outer diameter is 5/16" inch and the width is 9/64" inch, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease.