The Shortening Reserve Tank is a safe speedy way to insert shortening into a Donut Robot ® Mark II, Mark II GP, Mark II Gas, Mark II GP Gas, Mark V, or Mark V GP. Add solid or liquid shortening to the tank, which melts solid shortening and warms it. When the fryer needs shortening, a simple push on the valve adds enough to top it up. Not needed if you already have EZMelt Melter Filter.