4 x 10 x 4 Sealed Ball Bearing One Bearing 4 x 10 x 4 Sealed Ball Bearing, this is a popular size that could be used in many application that uses this size 4mm x 10mm x 4mm. Bearing is made of Chrome Steel, each bearing is rubber sealed from both sides to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.