Series DuoVent High Capacity Air Vents with Manual Vent Feature are used in commercial and residential hydronic heating applications to provide automatic air venting for hot or cold water distribution systems. It consists of a brass body construction with female NPT connection, brass cover, air vent with silicone rubber seal, shutter, polyethylene float with valve plug, automatic vent with black cap, and manual vent with red cap. Series DuoVent has a high capacity and high temperature rating and is ideal for use with glycol systems or for use as an anti-vacuum device. Can be disassembled for inspection and cleaning.