4 x 7 x 2.5 Shielded Ball Bearings One Bearing 4 x 7 x 2.5 Shielded Ball Bearings, Bearings are made of Chrome Steel, Bearing inner diameter is 4mm, Bearing outer diameter is 7mm and Bearing width is 2.5mm, each bearing has Double Shielded to protect the bearing from dust or any possible contamination.