Neptune's Series 500 Hydraulic Metering Pumps are perfect for metering applications. Each pump features a variable Oil By-Pass™ stroke adjustment which will allow better valve performance than variable linkage designs. The valve checks have extra time to seat even in heavy liquids since they are idle during the by-pass portion of the suction and discharge strokes. Series 500 pumps are available in Simplex and Duplex configurations and capacities can transfer up to 94 gallons per hour.