This 160mm castors are made of a zinc plated housing which ensures the castors are robust enough and suitable for a variety of environments. The swiveling castors, rotates in 360 degrees, and along with the white nylon wheel, this caster is strong robust and durable and suitable for moving machinery and equipment. The white nylon wheel in these castors, contains roller bearings making it easier to move whilst maintaining core strength. Nylon Castors - 160mm Nylon Swivel Castors