Selkirk 104800 Round Type B Gas Vent Top, 4", 4RVRTThe RV line of Selkirk round vent pipe and fittings is designed for use on approved gas appliances in residential and light commercial and industrial applications. Round vents for large appliances will be found in the QC section which follows. Size 4" Part No. 4RV RT Measures: 8" x 4 14" These tops cannot be used for wood burning applications Helps prevent rain and debris from entering the vent External screen prevents entry of most bird species