Special low-profile design works in close quarters on GM Ford and Chrysler vehicles where there is limited clearance between the fuel line fittings and fuel filters fuel rails or sending units. The tool is designed to access the center port on the GM fuel tank sending unit. For 3/8" and 1/2" applications. Will also service 2001 - current 3/4- and 1-ton trucks with the Duramax diesel engines.