6904-2RS Ball Bearings 20mm x 37mm x 9mm Lot of 10 Bearings Pack of 10 Ball Bearings 6904-2RS, this is a popular size that could be used in many applications, each bearing has 2 rubber seals to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease, bearings are made of Chrome Steel.