The Cusco rear sub-frame brace for the 1997-up Impreza/WRX/STi (GC8, GDA, GDB) offers increased performance two different ways. The first is by stiffening up the rear sub-frame of the Impreza by connecting both sides of the body. Secondly, the brace can be used with the bracket kit to retrofit the ’06 STi diffuser on the older Impreza models to help with aerodynamics. Be sure to check out the bracket kit, diffuser and diffuser bolts to complete the retro-kit!