Four sizes provide a tank to accommodate virtually all sizes of black water tanks and the storage area in any RV. Each 4-Wheeler is equipped with a heavy-duty, 3 Inch conventional sewer valve for ease of use and dependable performance. 4-Wheelers are available in 16, 25, 32 and 42 Gallon capacities. They are constructed from blow molded polyethylene, zinc plated steel and aluminum. The front mounted double wheel swivels for easy maneuvering and is mounted on a heavy duty, extra large mounting plate. Each 4-Wheeler is completely assembled.