The Inflatable Dock Wheels come in multiple sizes (9 in., 12 in., & 18 in.). The smooth-rolling wheels offer substantial dock cushioning. Features molded-in valves to adjust the level of firmness. Made from heavy-duty hot-dipped galvanized hardware. The wheels mount securely to the dock. The wheels guide boats into your slip easily. Regardless of wind and current conditions. Integrally molded ribs both top and bottom of these wheels make them valuable dock and boat protection and formidable guards against impacts.