Selkirk 104080 Universal Female Adapter, 4", #4RV-UAFThe 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 UAF For type B gas vent Allows metalbestos B vent connectors to be used in conjunction with other brands of existing vent Used to adapt to metalbestos pipe toward appliance. NOTE: Female