Features: These bearings are made of high quality steel for low noise and long service life. They are rubber sealed to avoid contaminants entering and save lubricant. Bearings have a 20mm inner diameter, a 42mm outer diameter, and a 12mm thickness. These are great for small hobby 20mm shaft/rod projects. There comes total 10 pieces miniature bearings which you may use for many different projects. Specification: Model: 6004-2RS1 Material: Bearing steel Type: Deep-groove high-speed Rolling Element: Single row Inner Diameter: 20mm / 0.8in Outer Diameter: 42mm / 1.7in Thickness: 12mm / 0.5in Quantity: 10pcs Weight: 339g / 12oz(approx.) Package list: 10 * Bearings Package List 1These bearings are made of high quality steel for low noise and long service life. 2They are rubber sealed to avoid contaminants entering and save lubricant. 3Bearings have a 20mm inner diameter, a 42mm outer diameter, and a 12mm thickness. 4These are great for small hobby 20mm shaft/rod projects. 5There comes total 10 pieces miniature bearings which you may use for many different projects.