TFXNPB Nitrogen Purge Tool-Hvac Nitrogen Purge Regulator Adapter for Purging and Brazing Refrigeration Tube, Nitrogen Purge Boot Regulator with Multi-Size O-Ring Seal(Orange). Hands-Free Nitrogen Purification: The tfxnpb nitrogen purge boot regulator is specifically designed to connect nitrogen regulators to refrigerant lines during brazing.