Test for clogged or obstruucted catalytic converters and mufflers. Fast and easy to use. Threads into Oxygen Sensor Port. Kit includes 12MM and 18MM adapters to fit most domestic and imported vehicles. Gage measures 2-1/2″ diameter and has dual scale: 15 PSI and 1.00KgCm2. Hose is 41″ long. No need to tap into exhaust system then reseal holes afterwards. Packed in a vinyl pouch for store display and tool box storage. Complete with instructions.