well the hydro farm fans are crap,i have a 6 inch that barely made it through one grow as a simple exhaust for room temp air, hydro farm is a local company for me and both of my friends stores will not stock most of there products,they do make good long lasting cheap water pumps though but thats about it.the impeller in my hydro farm became unseated,it came with a warranty but when i spoke with the rep he asked how i had it mounted,he told me that because it was hung with bunjee cords "to eliminate vibration" that my warante was void because i didnt follow proper mounting directions wich is bulls shit,i mean if you have the cash pick up a vortex,but honestly your using cfl's your not running hps lights so you can get a away with using a much smaller cfm rated fan,however u need to remember that when you add ducting and have any sort of bend in your ducting,like say...a 2 45 deg,and one 90 deg bend you just lost power out put on your fan and it decreases your cfm numbers,my general rule of thumb,is get 4X the amount cfm need for your exhaust and find the fan that is closest to that number,it saves a lot of hassle.