After you have your rack built, you can give Rich (www.reptilebasics.com) a call and he will go over with you, what route best suits your heating needs as far as what size flexwatt and how much, he will even wire it for you so that all you will need to do is stick it on the inside of the back panel of your rack (back heat) or loop it through your shelves for belly heat! Hope this helps, i get all my flexwatt from Rich he has never let me down!