4'' 90 Degree Dryer Vent Offset Elbow Dryer Vent 4" Dryer Offset Elbow - Here's a line of 4" rigid aluminum dryer vent pipe to use when replacing vinyl ducts. Use the dryer offset elbow when working with a difficult outlet. Note; Do NOT use more than one offset elbow per installation. See all 4" Dryer Vent Components.