Unit is fully automatic with preset sample modes from low through high flow sampling. Use with a Solinst Model 407 Bladder Pump or 408 Double Valve Pump for effective VOC and low-flow groundwater sampling. Ideal for use with Bladder Pumps, 99 customizable sampling presets. Use in automatic or manual mode. Unit is available in 125 psi or 250 psi versions, and uses 4 AA alkaline batteries that last up to 100 hours of normal use.