... connect to duct, no affect airflow. 4" high efficient duct muffler 1.uses,reduce the ... on the air power equipment (such as fan, air compressor, boiler vent, generators, water ... inquiry. Product informationRemarksProduct name Efficient Duct mufflersize 4" miniDuct mufflerFine structure ,Practical, Strong, ... working environment2.ues for air power equipment (fan, air compressor, boiler vent, generators, ...