when are these suggested to use

 

when you have a camber issue you can't fix.

 

Camber is not adjustable on the solid front axle. With bigger tires it becomes more of an issue. Get an alignment and see how far from zero degrees you are.
My tires kept wearing on the inside.
I installed a 1 degree ball joint on my left side and a half degree ball joint on my right side.
Now my tires are perfectly straight. I got the adjustable ball joints from Fast Undercar.

 

there is a little adjustment screw that is supposed to adjust the camber on the d30 knuckle, idk if it actually works