These 200mm nylon castors are made of a zinc plated housing which ensures the castor is robust enough and suitable for a variety of environments. The swiveling castors, with the white nylon wheel 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 - 200mm Nylon Swivel Castors