Description: Miniature ball bearings are available ball bearings of quite small size. These miniature ball bearings have a 3mm inner diameter, a 8mm outer diameter, and a 4mm thickness. Ball bearings of this size are ideal for precision work and applications that require a lot of functional mechanical parts in a small space, such as 3D printer, quadcopter or model. Features: These miniature bearings are made of high quality bearing steel for low noise and long service life. They are double shielded to avoid contaminants entering and save lubricant. Bearings have a 3mm inner diameter, a 8mm outer diameter, and a 4mm thickness. These are great for small hobby 3mm shaft/rod projects such as 3D printer, quadcopter or ship model. There comes total 10 pieces miniature bearings which you may use for many different projects. Specifications: Material: Bearing steel Inner Diameter: 3mm / 0.12" Outer Diameter: 8mm / 0.31" Thickness: 4mm / 0.15" Quantity: 10pcs Package Includes: 10 x Bearings Package List 1These miniature bearings are made of high quality bearing steel for low noise and long service life 2They are double shielded to avoid contaminants entering and save lubricant 3Bearings have a 3mm inner diameter, a 8mm outer diameter, and a 4mm thickness 4These are great for small hobby 3mm shaft/rod projects such as 3D printer, quadcopter or ship model 5There comes total 10 pieces miniature bearings which you may use for many different projects