The Viking Model FE90 Handline Eductors are an inexpensive foam proportioning device which use the Venturi effect to mix the correct amount of Foam Concentrate into the water supply, creating a Foam/Water solution. The Handline Eductors control the rate of mixture at 1%, 3%, or 6% using an internal metering orifice. Other than flowing water, no external power supplies are required to operate Handline Eductors