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 1.8mm deep U groove that generally ride on a rail or track. These are bearings that are used in many linear motion systems. There comes total 10 pcs bearings which you may use for many different projects. Specifications: Material: Carbon steel Model: U624ZZ Inner Diameter: 4mm / 0.15" Outer Diameter: 13mm / 0.51" Height: 7mm / 0.27" U groove Width: 5.2mm / 0.2" U groove Depth: 1.8mm / 0.07" Quantity: 10pcs Package Includes: 10 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. Package List 1These bearings are made from high quality carbon steel for durability and long service life 2They are double shielded to avoid contaminants entering and save lubricant 3Bearings have 1.8mm deep U groove that generally ride on a rail or track 4These are bearings that are used in many linear motion systems 5There comes total 10 pcs bearings which you may use for many different projects