It's a product from Humboldt County's own that stops upward growth and causes more of the lateral branches to get bigger and "bushier" for lack of another term. It claims to do this by changing some pathway within the plant to cause it to focus it differently. I'm not sure how it works, but you can see from the flowering plants in my pics that it caused about 7 rather large tops to grow at close to the same height. I didn't get much upward growth while flowering after I used it, so I think it does what it claims. Also those babies yielded about 45g/plant and they were only 24" tall. I think I'll be using it again since I have a height restriction. I posted a thread about it before I used it, if you just search for Bushmaster you can see what some others had to say.