8 x 12 x 3.5 Flanged Stainless Steel Ball Bearings, this is a popular size that could be used in many RC Cars and Trucks or any application that uses this size 8mm x 12mm x 3.5mm, 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.