The Brix is a proportioning device which pumps two liquids (e.g. water and concentrate) in an exact ratio. The particular ratio is determined in the pump, and is maintained precisely, independent of system flow or pressure changes, with no need to set or readjust. The pump operates on the source pressure of one of the proportioned liquids, typically incoming water, eliminating the need for CO2 pressurized air or electric power. NSF approved Model Description 94-260-21 Water Driven Proportioning Pump 3:1 ratio, EPDM seals and valves, Santoprene® diaphragm, 50 PSI, 3/8" barb fittings 94-260-22 Water Driven Proportioning Pump 5:1 ratio, EPDM seals and valves, Santoprene® diaphragm, 50 PSI, 3/8" barb fittings