18" Smooth Rolling Wheel Offers substantial dock cushioning and features molded-in valves to adjust the level of firmness. Heavy-duty Hot Dipped galvanized hardware mounts securely to the dock. Guides boats into your slip easily, regardless of wind andcurrent conditions.Integrally molded ribs both top and bottom of these wheels makes them valuable dock and boat protection and formidable guards against impacts. - cis2:mm5mnJlm -Specifications: Color: White; Box Dimensions: 11"H x 18"W x 20"L WT: 19.1 lbs; UPC: 776113950777; Owner's Manual (pdf)