For most LSx header installs we often recommend customers reuse the GM Gaskets that come on the car from the factory. This is because the factory gasket is a premium multilayer metal shim, which requires no sealant, and lasts practically the life of the car. Even in a used state, the factory gasket is superior to the cheap single layer steel, copper, or paper gaskets most aftermaket headers come with. On our own GTO, we still have the GM factory gasket through 4 different header installs! For customers who have damaged factory gaskets, or insist on all new hardware for their install, we are excited to now offer these same Genuine GM gasket. These are the same gaskets that come from the factory on the LS1, LS2, LS6, and most truck V8's. While these round port gaskets are not port matched to the D-port LS3 and LS7, they will still fit fine without obstructing exhaust flow.