Uniweld UNF3 Nitrogen Flow Indicator with 1/4-Inch Female Flare Inlet Connection and 1/4-Inch Male Flare Outlet Connection Nitrogen Flow Indicator, 1/4 Inch Female Flare Inlet Connection, 1/4 Inch Male Flare Outlet Connection Provides extremely low pressure (3 to 4 CFH) precision gas flow control for nitrogen purging applications Nitrogen Flow Indicator uses a float ball to visually confirm the nitrogen is flowing during the brazing of copper tubing in HVACR systems Maximum Inlet Pressure 50 PSI Over Pressure Safety Relief Rupture Disk