The Lisle 19mm and 22mm Line Sockets, No. 12320, are designed to replace fuel line fittings on Cummins ISB and ISX engines. The sockets help reduce the possibility of fuel leaks and prevent damage to fitting, fuel rail and fuel line. The 22mm is used on the ISX Cummins motors and the 19mm is found on 2011 and older diesel engines. These sockets are for use with a 3/8" square drive.