Top quality product These ball bearings are made of high quality steel for low noise and long life They are double sealed to keep contaminants out and save lubricant Bearings have an inside diameter of 6mm, an outside diameter of 12mm, and a height of 19mm < p>They are great for small hobby projects such as 3D printers, engraving machines Features: Top quality product. These ball bearings are made of steel high quality for low noise and long life. They are double sealed to keep contaminants out and save lubricant. The bearings have an inside diameter of 6mm, an outside diameter of 12mm and a height of 19mm. They are perfect for small hobby projects with 6mm rod such as 3D printers and engraving machines. Color: Black + Steel Features: Material: Steel bearing. Inner diameter: 6 mm. External diameter: 12 mm. Height: 19 mm. Quantity: 8 pieces. Note: The data is all measured manually, please allow 1-3cm error, due to the difference in light and display, there will be a certain color difference, the object actual received shall prevail.