Unique piston design opens inductor plate, reducing overall diameter when lowering or raising. Due to this patented design, no air is trapped between the inductor plate and the ink, eliminating the need for both the bleeder valve (except on initial start-up) and a hold down mechanism for the container. Works with 5 gal. or 3.5 gal. metal or plastic containers. With a new container in place, simply lower the inductor plate and upon contact with the ink the piston will close forcing the inductor plate to the container wall forming a perfect seal with no trapped air.