Introducing our Freedom Series cylinder heads for the 2017 2023 L5P 6.6L Duramax Each cylinder head is manufactured in our state of the art Freedom Racing Engine shop and is guaranteed to meet or exceed factory specifications. All heads are meticulously inspected, pressure and leak tested, and are equipped with new valves, valve guides, springs, and valve seals. Perfect for the daily driver or towing application. No core charge Features Re manufactured OE casting New valves, valve guides, springs, and valve seals Pressure and leak tested Multi angle valve job Installation Notes We recommend using GM head gasket Grade C, 12727486