Unless your car is dropped more than 1.5" there is no chance that you'll need it. What they do is make the lower mounting bolt on the strut a slightly adjustable cammed bolt so that you get that last little bit of adjustment you need to keep the camber within factory spec.
Unless of course it is a new top mount for the strut, in which case it is great for making pretty wide adjustments if you use the car for track racing. You can dial in a lot of negative camber for cornering and then dial it back out for use on the street and longer tire life.
