Subaru Technica International has designed this replacement for the OEM Trailing Arms. This kit replaces all the original rubber bushings with pillow ball (spherical) joints allowing for smooth and accurate movement of the suspension. They are also substantially stiffer, so your rear suspension is able to work more efficiently due to less deflection under hard cornering and bumps.
When matched with the STi Lateral Link Set, the result is a smooth and precise movement of the rear suspension.