Cummins TAIL PIPE and EXHAUST KITS – HGJAB RV generator sets have a built-in USDA Forest Service approved spark arrester muffler. It is necessary to equip the generator set with a tailpipe at installation. Contains tailpipe, clamp and a hanger. Exhaust tube connects to 1-3/8 inch Outer Diameter down tube on generator. 26 Inch Tailpipe.