This air gap is used with reduced pressure zone assembly models, 3/4 to 1 IN 825 and 1/2 to 1 IN 860 series. Made of durable black composite material. The air gap provides an unobstructed, physical separation between the discharge 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. Can be installed vertically or horizontally (vent elbow required for vertical installation)