Features [ACCURATE SIZE] The set contains 10 pcs linear ball bearings for use, with inner diameter of 12mm, outer diameter of 21mm and height of 30mm. [HIGH STRENGTH] These linear motion ball bearings are made from alloy steel, with high tensile strength and hardness. [LASTING LIFE] Alloy steel linear motion bushings are resistant to damp, corrosion, acid and rust, ensuring lasting use. [LOW FRICTION] The linear bearings have smoothly surface, low noise, low friction coefficient and high track accuracy. [WIDE USAGE] Cylinder linear bearings are suitable for industrial automation equipment, such as 3D printer, engraving machine, XYZ module, etc. Specification: Item Type: Linear Ball Bearing Material: Alloy Steel Model: LM12UU Inner Diameter: Approx. 12mm/0.5in Outer Diameter: Approx. 21mm/0.8in Height: Approx. 30mm/1.2in Use: Widely used in various industrial fields such as machine tools, construction machinery, robots, speed reducers, steel, metallurgy, textiles, mining, printing, aerospace, and so on Package List:10 x Linear Ball Bearing Package List 10 x Linear Ball Bearing