6903ZZ Shielded Ball Bearings 17mm x 30mm x 7mm 6903ZZ Shielded Ball Bearings, the inner diameter is 17mm, outer diameter is 30mm and the width is 7mm, 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 made of Chrome Steel, Bearings are packed 10 bearings in one plastic tube.