All Welch Self Cleaning Dry Vacuum Systems are constructed with PTFE heads, perfluoro-elastomer valves, and a PTFE coated, molded diaphragm. Advanced Vapor Management (AVM) for vacuum control, a vacuum readout, and instant-response bumping/foaming switching are standard on all models. Inlet and outlet separator traps and hose barbs are fitted. Standard vacuum digital readout units are mBar.