need cheap exhaust check mine out!! $11 @target

just bought this fan and customized it to work in its box sort of like a can fan to exhaust heat out of grow cab, all for $11, and some duct tape, i was going to buy 2 4" computer fans from radio shack but they were $20 a piece, plus i had to make a ac/dc adapter

Yep I've reccomended those before... They move a lot of air for the money.