The Mueller-Kueps Sensor Tap Kit, No. 506 021, is designed to professionally restore the NOx sensor hole thread without damaging the exhaust system. The tools are for sensors sizes M20x1.5 and M22x1.5. Coarse carbon deposits are removed by the guide pin with cleaning grooves. Measuring just 27mm in length, the extra short tools can be used in extremely tight spaces. Each tool features hard material coating, six cutting edges for ideal centering, and integrated guide pins for recutting dirty holding threads, especially for NOx and particle filter sensors on exhaust systems. Made in Germany.