The Model 408 Double Valve Pumps are positive displacement, gas drive pumps providing high quality, consistent samples, and excellent VOC (Volatile Organic Compound) sample results. Pumps are available in stainless steel 5/8" diameter, and 1.66" diameter. Portable or dedicated versions are available. They can be fitted with packers to control groundwater flow and limit purge requirements. DVPs are easily disassembled for decontamination in minutes, without any tools.