There are two carbon steel ball bearings inside the pulley, which can reduce the friction of the wheel. The pulley turns more flexibly and has no noise.Stainless steel manufacturing, rust - proof, - , outdoor use can also prevent pulley .Compared with other pulleys, pulley wheel support plate is thicker, the wheels are stronger and the bearing capacity is stronger.Pulleys are removable for easy installation. A single small pulley can carry 660lb/300kgSpecificationProduct Name: U Type PulleyColor: SilverMaterial: 304 stainless steelInstallation height: 54mm(2.125in)Wheel diameter: 48mm(1.889in)Wheel thickness: 22mm(0.866in)Groove width: 16 mm(0.629in)Groove depth: 7 mm(0.27in)Product weight: 280g(0.617lb)Load: 300 kg (660 Ib)ApplicationGenerally used as a rail wheel Grooved WheelPackage Contents:1pcs * U-Type PulleyOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.jj