1、These miniature bearings are made of high quality bearing steel for low noise and long service life 2、They are double shielded to avoid contaminants entering and save lubricant 3、Bearings have a 4mm inner diameter, a 9mm outer diameter, a 4mm thickness and a 10.3mm flange 4、These are great for small hobby 4mm shaft/rod projects such as 3D printer, quadcopter or ship model 5、There comes total 10 pieces miniature bearings which you may use for many different projects Description: Miniature flanged ball bearings are available ball bearings of quite small size. These miniature ball bearings have a 4mm inner diameter, a 9mm outer diameter, a 4mm thickness and a 10.3mm flange. 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 4mm inner diameter, a 9mm outer diameter, a 4mm thickness and a 10.3mm flange. These are great for small hobby 4mm 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: 4mm / 0.15" Outer Diameter: 9mm / 0.35" Thickness: 4mm / 0.15" Flange Diameter: 10.3mm / 0.4" Quantity: 10pcs Package Includes: 10 x Bearings