Ball Bearings 6906ZZ 30 x 47 x 9 mm Lot of 10 Bearings 10 Ball Bearings the inner diameter is 30, outer diameter is 47 and the width is 9, this is a popular size that could be used in many applications, Bearings are made of Chrome Steel and can rotate up to 19000 rpm, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease.