Product Type Venting For Gas Heaters Compatible with Product Type Dayton Infrared Tube Heaters Opening Height 4 in Opening Width 4 in Mounting Type Flange-Mount Vent Direction Horizontal Vent Length 5 5/8 in Vent Diameter 4 in Vent Size 4 in Vent Type Direct Vent Flapper Length 4 in Flapper Width 4 in Material Galvanized Steel Outer Diameter 4 in Overall Length 5 5/8 in Includes Flapper Standards UL Listed