6706ZZ Shielded Ball Bearing 30mm x 37mm x 4mm 6706ZZ Shielded Ball Bearing, Bearing inner diameter is 30mm, Bearing outer diameter is 37mm and Bearing width is 4mm, 6706ZZ bearings is a popular size that could be used in many RC Cars and Trucks, Bearings is made of Chrome Steel, each bearing has 2 metal shields to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease.