Miniature Ball Bearings are small bearings with balls as their rolling elements. These small bearings are made of Chrome Steel and can rotate up to 15000 rpm, each bearing has 2 Premium Rubber Blue Seals to protect the bearing from dust or any possible contamination, Our bearings are manufactured for engineered shafting, bearings are pre-lubricated with Mobil Polyrex grease EM. These bearings are ABEC 3 Quality.