SMR137-2RS Stainless Steel Ball Bearing 7mm x 13mm x 4mm SMR137-2RS Stainless Steel Ball Bearing, bearing is made of Stainless Steel, SMR137-2RS is rubber sealed from both sides to protect the bearing from dust or any possible contamination, also bearing is pre-lubricated with grease, the inner diameter is 7mm, the outer diameter is 13mm and the width is 4mm.