Explain: 1. Made of high-quality materials, durable and practical. 2. Don't expand only when the extension doesn't work. This is the built-in real Mini catalyst. 3. When the catalyst is removed, the rear oxygen sensor will display higher temperature and higher flow of unburned fuel. 4. As a result, this throws a check engine light (unit, SES, DTC) with error codes typically p0420 (catalyst system efficiency below threshold library 1) and or or p0430 p0420 catalyst system efficiency below threshold library 2). Off road only . Specifications: Size: about 46.5x16mm Size: external thread M18x1.5 internal thread M18x1.5 length 46.5mm Material: Stainless steel Package list: Oxygen O2 Sensorx1 Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.