Left.3.6 LITER. Preconverter nut. Right.3.6 LITER. A solid metal or plastic block with a threaded hole in the center which is used to tighten or adjust the Exhaust System Hanger. Catalytic Converter Nut. Exhaust Flange Nut. Exhaust Muffler Nut. Exhaust Pipe Nut. Catalytic cnvrtr. Connector. Converter. Flange. Hanger U -. HexAGON. Muffler. PreConverter. Support. System Hanger.