Originally Posted by M.Bonanni

Basically they are length adjustable so you can set them up to have no preload on the bar when the car is sittings still. So to install them correctly you have to connect them to the sway bar while the car is sitting on the ground or on a set of wheel blocks or something supporting its own weight. Then adjust the length of the end link to meet the sway bar. If you attach it while the car is off the ground and the suspension is unloaded then when it gets back on the ground there is already stress and pressure on the links while the car is just sitting there, even more pressure when the bars start to move under the load of cornering. That's the whole reason aftermarket links are length adjustable and not just stronger versions of the stock links. Setting them up properly also helps maximize the effectiveness of the sway bar.