6904ZZ Shielded Ball Bearings 20mm x 37mm x 9mm 6904ZZ Shielded Ball Bearings, the inner diameter is 20mm, outer diameter is 37mm and the width is 9mm, Bearings are made of Chrome Steel, 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 packed 10 bearings in one plastic tube.