6000-2RSN Deep Groove Ball Bearing. the inner diameter is 10mm outer diameter is 26mm and the width is 8mm. The bearing has 2 Rubber Seals to protect the bearing from dust or any possible contamination also bearing is pre-lubricated with grease, 6000-2RSN Bearing is made of Chrome Steel, 52100 is a high carbon, chromium containing low alloy steel, heat treatment and hardening of 52100 alloy steels will get you 60 Rockwell hardness and very common in bearings.