Reaper Diesel Water in Fuel sensor wrench for 2001-2016 Duramax and 2013-2018 Cummins. When replacing the fuel filter on a 2001 to current Duramax, the water-in-fuel sensor located in the bottom of the filter must be removed and reused in the new filter. 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 6 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. The 42mm side will also work on 2013-2018 Cummins filter that is located under the bed.