no,those are the lengths of ducting,3ft &4ft.they are both 6 inch ducting,no reducers or anything.the fan and the hood are 6 inches as well. i have an htg easy cool 6 hood,starting to think maybe it's the cause but i don't know for sure.i may end up getting a supersun 2 or something with better flow. nugs are still looking great btw bro,thats one expensive skull lolgraham-i think its because ur restricting the flow of ur fan by reducing it so much,if u just use 6 inch duct i bet ur good to go...im assuming tht fan is atleast a 6 inch w all them cfm's...just a guess.