The inner diameter is 20mm, outer diameter is 32mm and the width is 7mm, Bearings are made of Chrome Steel, also bearing is pre-lubricated with grease, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination. Item: 6804ZZ Ball Bearings Dimensions: 20mm x 32mm x 7mm/Metric Bearing Inner Diameter: 20mm Bearing Outer Diameter: 32mm Bearing Width: 7mm Size: 20 x 32 x 7 mm Dynamic load rating Cr: 4,000 N Static load rating Cor: 2,640 N Limiting Speed: Grease Lubrication: 13,000 RPM