These shopping cart wheels are made of high-quality, wear-resistant polyurethane material, ensuring excellent durability and wear resistance. With a load-bearing capacity of 1000LB, these wheels are perfect for a wide range of applications such as grocery carts, hand trucks, and trolleys. They come in a perfect size design of 4 inches in diameter and 1.25 inches in width, with a bore size of 5/16'' to 3/8''. The wheels also feature double ball bearings for smooth and silent operation. Additionally, they are resistant to most chemicals, solvents, acids, and oils, ensuring they won't corrode or disintegrate in any environment. If you have any questions or concerns, please don't hesitate to contact us.