Weather Cap 3 1 4" - 3 7 16" For Universal ProductsOne New Aftermarket Replacement Exhaust Weather Cap Rain Cap 3 1 4" to 3 7 16" Pipe O. D. This exhaust weather cap (rain cap) mounts over the top of a vertical exhaust stack to keep rain, snow, dirt, dust, and debris from entering the exhaust pipe when the engine is not running. The hinged, counterbalanced cover opens under exhaust pressure and closes automatically at shutdown. Fits exhaust pipes with an outside diameter of 3 1 4" to 3 7 16".