These bushings connect the four rear lateral links to the subframe and the knuckle. You can find a bolt kit for the lateral links here.
There are four different bushings -- specify front/rear and inner/outer. Sold individually, so you'll need two of each (eight total) if you want to do all four links. Yes, they are all very similar in appearance. They ARE all different part numbers. We're not sure why the prices diverge so much.
Fits all 2002-2007 Subaru Impreza/WRX/STI.