Someone please help me as i DO NOT understand, i wan't to get an inline extractor fan my grow tent has 2 vents measuring 5.1inches. Do i need a 5inch fan for the 5.1inch fitting? How does it work, i will have the fan and the carbon filter in one vent, off the filter ducting since i don't have a reflect or air cooled hood just the bulb will i just have the ducting running from the carbon filter to the other vent? surely this will just run air from outside the tent through the ducting and into the fan which will be pointless as it will just be fresh air anyway and not the cannabis smell? If i was to get a normal reflector not an air cooled hood how would i attach the ducting to it??