New Fel Pro performance gaskets. These intake gaskets would go between the LS1/LS2/LS6 aftermarket aluminum intake and the cylinder heads (cathedral port) when using aftermarket aluminum intakes that do not accept o-ring seals grooved into the intake, whereas the intake flange is totally flat and machined. Gasket is .030" thick.  Sold as a pair (2 gaskets).  You should be using a feeler gauge to ensure you need gaskets this thin.  This is the thinnest set offered, typically used with very thick head gaskets.