A. It has sealed 6200ZZ ball bearings. B. It is suitable for residential and commercial doors and fits 2 - inch tracks. C. The load - bearing capacity of a single roller is 150 pounds after 100,000 cycles. D. The nylon material can reduce noise. E. It is durable. F. There is a nylon shell around the wheel, which runs quietly. G. Specification parameters: - Wheel thickness: 0.48 inches - Wheel diameter: 1.8 inches - Length: 4.78 inches - Shaft length: 4.25 inches - Shaft diameter: 0.43 inches - Color: Black - Material: Nylon + Metal H. Package contents: - 12 garage door rollers - Only the above - mentioned package contents are included, and other items are not included. I. Attention: Light and different displays may cause the color of the item to vary slightly from the actual object. The measurement tolerance is +/- 1 - 3 cm.