Im guessing it's like sissy squats. You only godown as the movement implies, a quarter of the proper squat movement. Apparently, it hits the teardrop etc and the muscles insertion nearer the knee. I have no idea if it works, I don't think they are worth it, just do all leg exercises with FULL range of motion and you'll hit all the parts of the thigh IMO. Think Zane and Tom Platz used to swear by them (can't really argue with platz when it came to legs), so maybe they do work, I don't know.