Sway control and it prevents bottoming out. I still haven't done the free travel mod on my truck, just a half dozen other people's. The helper springs act as a bumpstop, mine lift the truck 1/2' with 7psi or so but it's worth the added height for the improved handling and ride improvement.how neccesary would you say those airlift helper bags are? or is that just a recomendation for those who already have the autoride?