2007-I to current diesel engines have limited access to the fuel filter housing, which is mounted closely to the engine. Although a hex is cast onto the bottom of the housing, it may break if used to remove or install the fuel filter housing. A wrench that reaches all the way around the wrench will not fit, due to interference with the mount bracket, harnesses, or fuel lines. GM-50191 is open at one end and has multiple slots to engage the ribs on the outside of the filter housing. The square drive is also offset, allowing for additional installation clearance by turning GM-50191 over.