Like Horticulture420 says. most of the products contain Paclobutrazol, which you should care a bit about, if you are gonna smoke the end product.
I have used before and it stops vertical growth, and leaves you with ugly plants, that yields tight heavy nugs. Not bigger but heavier and denser than without.
I don't like using Paclobutrazol, and I would strongly advise peeps not to use it, as it releases lots of carcinogens when burned, supposedly.
I you have height issues, you need to learn to control and manipulate the plants growth.
Hell, they almost don't care if they are vertical or horisontal. Tie them down, use a net, supercrop them.