Thats a wrist wroller like in the link i posted: http://www.jumpusa.com/wrist.htm and its a great way to strengthen the wrists and forearms.
You are young, your body is still growing. Just get down to some old fashioned boxing training and everything will work out alright. By old fashioned I mean doing things like pushups on your fingers and knuckles. It is a low cost solution to getting in shape. It worked for Jack Dempsey and it will work for you.
attach an ankle weight around ur arm while u jerk off.....ull be burning and feel orgasmic. 2 for 1 deal
You will keep growing until you are about 20. Read the thread I posted earlier, BHOp has a 6" wrist and is an ATG.