Features: These bearings are made from high quality carbon steel for durability and long service life. They are double shielded to avoid contaminants entering and save lubricant. Bearings have 1.4mm deep V groove that generally ride on a rail or track. These are dedicated bearings that are used in many linear motion systems.There comes total 20 pieces bearings which you may use for many different projects. Specifications: Material: Carbon steelModel: V623ZZInner Diameter: 3mm / 0.12"Outer Diameter: 12mm / 0.47"Height: 4mm / 0.15"V Groove Angle: 90V Groove Width: 2.8mm / 0.11"V Groove Depth: 1.4mm / 0.05"Quantity: 20pcs Package Includes: 20 x Bearings Note:Please note that the new type and old type of this product will be sent randomly, and make sure you will not mind before ordering..