can anybody tell me what these do?

 

They have two purposes:

1. If you have a Lancer that did not come with a rear sway bar from the factory, the perches allow you to mount a rear sway bar.

2. If you have a Lancer that did come with a rear sway bar from the factory, these can be used to replace the stock perches, which are weak. They are also necessary if you upgrade the rear sway bar to the Progress sway bar sold through RRM, as the Progress bar has warped and broken the stock sway bar perches on peoples cars.