3974326 lubricating oil filter head covers many Cummins platforms including ISB, QSB, 4B3.9, 6B5.9, 6C8.3, B3.3, B4.5, ISC, QSC, ISL, QSL, L8.9, L9, L9.3 and L9.5. It serves as the mounting base for oil filter assemblies and guides lubricant flow routes. Solid casting construction prevents oil bypass and pressure fluctuation in lubrication circuits.