Ball Bearings 4x8x3 Stainless Steel With Ceramic Balls 2 Bearings 2 Stainless Steel Ball Bearings with Ceramic Balls , this is a popular size that could be used in many application that uses this size 4mm x 8mm x 3mm. Bearings are made of Stainless Steel, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearings are pre-lubricated with grease, Ceramic Balls are the highest standard of balls that can make your bearings live at least 5 times more than any other bearings.