ETS 2015+ Subaru STI Stock Turbo Intake Air Filter (SP-3860)

This SP-3860 filter is the replacement for the ETS 2015–2021 STI stock-turbo intake. ETS lists it for both stock-MAF and speed-density versions of that intake. I'd replace it when the existing filter is damaged, worn or no longer cleans up properly, keeping the intended filter fit and filtration. It replaces the filter on the ETS system rather than the factory airbox.