R1810ZZ Shielded Ball Bearings 5/16" x 1/2" x 5/32" inch 10 Bearings R1810ZZ Shielded Ball Bearings, Bearing inner diameter is 5/16" Inch, Bearing outer diameter is 1/2" Inch and Bearing width is 5/32" Inch, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease.