500-S Series Hydraulic Metering Pumps come standard in Neptune’s Simplex design, but can be converted to Neptune’s Duplex design - 500-D Series. Each pump comes with a variable Oil ByPass™ stroke adjustment feature which allows for better valve performance than variable linkage designs. The valve checks have extra time to seat even with heavy liquids since they are idle during the by-pass part of the suction / discharge strokes. Comes standard with 1/3 HP, 1ph, 115 VAC, 60C, TEFC motor with other options available. Materials of construction options include: 316 Stainless Steel, Carpenter-20, PVC or PVDF Liquid Heads & PTFE Diaphragms. Capacities range from 0.80 gph (3.03 L/h) to 34 gph (128 L/h). 3,000 psi (206.8 bar) maximum pressure on certain configurations. Maximum Temperatures: 316SS & C-20 - 200°F (93°C); PVC & PVDF- 125°F (52°C).