Fits 3/4 inch 009, 1 inch 009, 3/4 inch 909, 1 inch 909, 1 inch 009M2, 1-1/4 inch 009M2, 1-1/2 inch 009M2, 1-1/4 inch 995, 1-1/2 inch 995, and 2 inch 995 Series. This air gap for reduced pressure zone assembly, provides an unobstructed, physical separation between thedischarge end of a potable water supply line and an open receiving vessel. The installation of an air gap and drain line are recommended on reduced pressure zone assemblies. It can be installed vertically or horizontally (vent elbow required for vertical installation).