The 3903 and 3905 quick release valves allow for fast exhaust of air from lines, actuators and accumulators, and are constructed of die-cast silicon brass and stainless steel for long life in rugged environments.
The 3903 / 3905 have pipe port sizes of 1/4" and 1/2" NPT respectively, but also have exhaust port sizes of 3/8" NPT and 1/2" as well, with a recommended maximum operating pressure of 200 PSI (13.8 BAR).