Selkirk RV Gas Vent 90 deg. Adjustable Elbow is designed for use when an offset is needed to avoid obstructions such as rafters, joists, and other construction obstacles. This adjustable elbow allows you to easily orient the pipe between vertical and horizontal positions, providing flexibility in installation. It features a four-piece adjustable elbow that twists for easy offsets, accommodating different size requirements with the inside diameter referring to the pipe or fitting size. The outside diameter of the RV vent is approximately 1/2" larger. The product comes in various sizes including 3", 4", 5", and 6", each with a durable aluminum liner and galvanized steel jacket. It is UL Listed and rated for temperatures up to 550°F, ensuring safe and reliable performance as a Type B gas vent. Model Number: 3RV-EL90