These adapters bolt on to your OEM rear 1 pot backing plate to allow you to bolt up Subaru/FHI 2 pot calipers adapters or 04-07 STI Brembo 2 pot rears.  Note: this only adapts the calipers. You will need the appropriate rotors and for Brembos you will either need modified e-brake shoes or special rotors to utilize the e-brake.