10 Ball Bearings 61801ZZ 12 x 21 x 5 mm Lot of 10 Ball Bearings ( 61801ZZ ), the inner diameter is 12, outer diameter is 21 and the width is 5, this is a popular size that could be used in many applications, Bearings are made of Chrome Steel, each bearing has Double Shielded to protect the bearing from dust or any possible contamination.