High quality materials and craftsmanship Made of high quality carbon steel, smooth and resistance free, suitable for adjusting industrial transfer belts. Ball Transfer Units Material: Carbon Steel Color: Silver < li>Diameter (approx.): 70mm / 2.75" Mounting hole diameter: 55.5mm / 2.18" The maximum load: 35kg< /li> Package includes: 4 * Ball Transfer Units Be sure to add lubricant during the maintenance period. Balls should be laid out horizontally and should have at least three (preferably four) balls. Please allow 1-3mm error due to manual measurement. Thank you for your understanding. Features: Convenient to install, flexible bearing, ideal for most industrial transfer applications. Suitable for electronics, hardware, mechanics, chemicals, food, supermarkets, etc. Protective cover ensures low torque and longevity.