2021 upgraded version with smooth polished surface, smooth operation, high efficiency and low noise. High temperature resistance, can work in the temperature range of about -20-200. Made of high quality bearing steel, it is strong enough for long-term use. Widely used in many fields: industrial machinery, automobiles, ships, home appliances, systems health, etc. 2 rubber seals prevent water and dust or other objects from entering. Features: The surface is polished and smooth, with high working efficiency and low noise. High temperature resistance, can work in the temperature range of about -20-200. Made of high quality bearing steel, it is strong enough for long term use. Widely used in many fields: industrial machinery, automobiles, ships, household appliances, health systems, etc. Specification: Material: bearing steel Model: 6001-2RS Color: Silver (as shown in the picture) Inner diameter: approx. 12mm/0.47in Outer diameter: approx. 28mm/1.10inch Thickness: approx. 8mm/0.31in Operating temperature: -20-200C Quantity: 10 pieces Weight: approx. 300 grams