When replacing the fuel filter on a 2001 to current GM Duramax light duty truck the water-in-fuel sensor located in the bottom of the filter must be removed and reused in the new filter. The SP Tools Duramax Water In Fuel Sensor Wrench, No. 13100, aids techs in completing this task. This wrench has two sides, one designed to fit the odd-shaped 40mm 12-sided sensor found on 2001 to 2010 trucks, the other end fits the 42mm six-sided sensor on the 2011 to current trucks. This sensor is made of plastic and easily damaged by using pliers and other nonspecific designed tools, so using the correct tool is a must.