Bearing Sealed 5x12x4 Miniature5 x 12 x 4 Sealed Ball Bearing One Bearing 5 x 12 x 4 Sealed Ball Bearing, made from durable 52100 alloy steel, commonly known as chrome steel, each bearing is rubber sealed from both sides to protect the bearing from dust or any possible contamination, also bearing is pre lubricated with grease, Bearing 5mm inner diameter, Bearing outer diameter is 12mm and Bearing width is 4mm. 5 x 12 x 4 Ball Bearing Deep Groove Ball Bearing Closures: Two Rubber