Neptune's 6000 Series Hydraulic Metering Pumps are designed for high-pressure, low-volume applications and are available in simplex or duplex. The pumps in the 6000 series are adjustable capacity by using the micrometer dial that can be varied while running or when stopped. Variable Oil By-Pass™ Stroke Adjustment provides increased valve performance in comparison to variable linkage designs. This performance improvement results from valve checks that allow extra time to seat even in viscous fluids since they are idle during the by-pass portion of the suction & discharge strokes. They also use a hydraulically balanced PTFE diaphragm to eliminate stress. Comes with 316 Stainless Steel Liquid Head & PTFE Diaphragm. Capacities range from 4.5 gph (16 L/h) to 28 gph (106 L/h). 4,000 psi (275.8 bar) maximum pressure on certain configurations. Maximum Temperature is 200°F (93°C).