Wheel-a-Weigh launching wheels for small boats and car toppers ride in tracks permanently installed on the transom. Wheels lock in the down position for transporting overland. After launching, they lock in the up position. Wheels are easily removed for storage or theft prevention. These units are sturdy made of anodized marine aluminum and stainless steel with injection molded wheels. Fully pneumatic tires. Wheel Dimensions: 16 x 4.0 inches (40.6 x 10.2 cm). Weight Capacity: 300 lbs. (136 kg) on hard surfaces, 200 lbs. (91 kg) in soft sand. Shipping Weight: 16 lbs. (7.3 kg).