Lowering a Subaru does more than just lower the center of gravity: it adversely effects suspension geometry, which results in increased body roll and less camber gain of the outside wheel during cornering. This is not good for handling performance or overall grip.
The Whiteline Roll Center kit uses taller ball joints and tie rod ends to correct the front suspension geometry on a lowered car (to a point). The results are less body roll, more front end grip, and an improvement in dynamic camber characteristics.
These are a must for any Subaru lowered an inch or more. Fits nearly all subaru models, full replacement for stock ball joints and outer tie rods. Some early (90-94) Legacys and Imprezas may need to change inner tie rods.