Selkirk 104082 Adjustable Pipe Round Type B Gas Vent, 4" x 12"The 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 AJ12 Length: 12" Used in combination with a straight length, this component assures that an exact required vent length can be achieved Allows for easy disassembly and can absorb the linear