Ball Bearing 6904ZZ 20 x 37 x 9 mm one Ball Bearings 6904ZZ, the 6904ZZ inner diameter is 20mm, the 6904ZZ outer diameter is 37mm and the 6904ZZ width is 9mm, 6904ZZ is a popular size that could be used in many applications, 6904ZZ Bearings are made of Chrome Steel, each 6904ZZ bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also 6904ZZ bearings are pre-lubricated with grease.