The R-K series back pressure regulator is designed to protect piping and equipment from pressure changes where a constant regulated pressure on the up stream side of the valve is required. Prevents pumps from dead heading, over pressurization, pressure surge conditions, and maintains back pressure in closed loop systems. Adjustable screw and lock-nut makes it easy to accurately pre-set desired relief pressure Teflon (primary) and EPDM (back-up) diaphragms standard. No Metal contact with fluid Wide adjustable relief pressure range (10-125 PSI) Small pressure differential band from cracking point to fully open, and from fully open to close. Top entry makes in-line maintenance quick and easy. Ideal for DI water, harsh chemical, and other high purity applications.