This is a check valve kit for the outlet of the exhaust which prevents the suck-back of exhaust vapors after the Edwards iGX Dry Pumping system is shutdown. The check-valve also provides additional attenuation of the pulses in exhaust pressure, for process N and M. Includes Exhaust Check Valve, Elbow, Trapped O Rings, Clamps and Insulation Jackets, for Edwards iGX Dry Pumps N and M models,