I thinkit's a 6" PC fan..the screw holes corner to corner. The fans running, I stoned, I like my fingers! LOL Know what I mean? and all that out of a grandpa!
Virtualsunhydroponics.com has good stuff for cheap. That's where I got my light setup and it works great. They did give me a broken mh bulb, but they replaced it fast and free, so I'll let them slide. But anyway, cheap cool tubes and whatnot