Perrin offers their rear sway bar in 19mm and 22mm diameters for the 2015 WRX. Both 19mm and 22mm Perrin rear sway bars are made from mandrel bent, solid 4130 steel and are sealed in an extra-thick powder coating for enhanced protection from the harsh elements. The bright-red finish on the Perrin sway bars adds a nice touch of color to your Subbie's suspension too. The Perrin rear sway bar kits include Perrin's polyurethane sway bar bushings that don't require frequent regreasing common in other bushings. Perrin's bars features multiple end link attachment points so you can fine tune the sway bar to compliment your other suspension components and your particular driving style.