The STH and STQ Duplex metering pumps from Fluid Metering are made for precision mixing, diluting, and proportional metering for OEM medical, analytical, and industrial instrumentation. The pumps consist of two FMI valveless pump heads direct coupled to a single variable stepper motor drive. The displacement of each pump head is independently adjustable, and a variety of pump head sizes can be used in combinations to achieve dispensing ratios from 1:1 up to 500:1. The metering pumps feature a valveless piston pumping technology and are the valveless-syringe alternative to conventional syringe pumps. The valveless pump design eliminates multiple syringes, valves, actuators, and drivers required by conventional syringe pumps for continuous fluid dispensing and metering. By eliminating valves and utilizing ceramic internals, the pumps will dispense millions of maintenance-free cycles at ±1% precision without recalibration. In addition, the pump has unidirectional continuous flow, utilizing two separate ports for input and output.