Varibell® is a rotary quarter turn valve. The regulating element is a bell shaped plug, featuring tear drop shaped apertures machined into both inlet and outlet but laterally reversed. During opening, this plug rotates and simultaneously uncovers the two tear drop apertures giving fine flow adjustment with a 2 stage pressure reduction across both seats.

As the plug further rotated the profiled apertures gradually become circular permitted an increasing flow. At full capacity the apertures are circular over the whole pipe diameter and the flow is unrestricted.

The bell shaped plug with a slope angle outside the interlock is being pressed into the valve seat by means of the spring force in the bottom cover.

During rotation the seat simultaneously acts as a "friction bearing", absorbing the friction forces over a wide surface area and centering the control element under the action of the spring.