10 Ball Bearings with Ceramic Balls, this is a popular size that could be used in many fishing reels, or any application that uses this size 3mm x 6mm x 2.5mm. Bearings are made of Chrome 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.