These bearings are made of high-quality carbon steel, durable and long life. They are double shielded to prevent contaminants from entering and save lubricant. It is usually installed on a rail or track. These are special bearings for many linear motion systems. A total of 10 bearings can be used for many different projects. el: 625zz bearing Colour: black Material: POM, carbon steel Size: diameter: 24mm Package Contents: 10 x BearingsOnly the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.