This is the OEM Subaru foam gasket found on the factory radiator. The seal helps direct the air through the radiator, and also cushions the radiator from rattling against the core support. This will also fit on aftermarket radiators like the Mishimoto pictured. (Radiator sold separately.)
Peel-and-stick installation.
Fits all 2015-2021 Subaru WRX and STI.