This is the Grimmspeed Header Collectors to Crossover Gaskets. Anytime that you perform maintenance that requires removal or maintenance of these particular components, you have to take notice if the existing gasket is still in good shape. The header collectors to crossover gaskets will endure more heat than any other gasket on the vehicle and even though these are typically made of metal, does not mean that they aren't immune to damage.
The Grimmspeed gasket has been fabricated from multi-layered steel materials and they have been designed with double thickness which helps promote optimal sealing to avoid the risk of an exhaust leak.
Sold as a pair.