The ARP is a modular style, direct operated precision regulator. A locking adjustment knob allows the pressure to be set, and then locked to prevent accidental setting changes. The ARP20/30/40 series is available with a back flow function that exhausts the air pressure in the outlet side reliably and quickly. Special applications include (10-) clean room compliant, (20-)copper-free, fluorine-free, and (21-) clean room compliant, copper-free, fluorine-free and silicon-free.