as standard the droplinks which hold the suspension arms if you like and allow them to move up and down and move slightly, are plastic
changing to perfoarmance ones, ie powereflex, whiteline or whatever which are metal will stiffen it up for you at the back and the front of the car giving you a firmer ride with more stability in the corners.
most people use whiteline and cost about40 sheets
i have powerflex which i think are better and cost 65
(rear only)