Features They are double shielded to avoid contaminants entering and save lubricant. These bearings are made of high quality steel for low noise and long service life. These are great for small hobby 15mm shaft/rod projects. Bearings have a 15mm inner diameter, a 21mm outer diameter, and a 4mm thickness. There comes total 10 pieces miniature bearings which you may use for many different projects. Features:These bearings are made of high quality steel for low noise and long service life.They are double shielded to avoid contaminants entering and save lubricant.Bearings have a 15mm inner diameter, a 21mm outer diameter, and a 4mm thickness.These are great for small hobby 15mm shaft/rod projects. There comes total 10 pieces miniature bearings which you may use for many different projects. Specification:Model: 6702ZZMaterial: High-carbon chromium bearing steelType: Deep-groove high-speedRolling Element: Single rowInner Diameter: 15mm / 0.6inOuter Diameter: 21mm / 0.8inThickness: 4mm / 0.2inQuantity: 10pcsWeight: 33g / 1.2oz(approx.) Package list:10 * Bearings Package List