Here's a spec sheet of the 4" the spec sheet for the 6" the carbon filters that would go with them are 4".. Airflow: 260 CFM (+/-5%) (Max) Suitable for: 7m3 6".. Airflow: 530 CFM (+/-5%) (Max) Suitable for: 12m3 As per the title im getting a 3.3'x3.3'x6.5' (square meter tent) i will have a 400w mh/hps setup. 6" hood reflector (24"x17"). will the 4" inline i posted be good for that setup in that tent with that size hood reflector or should i go with the 6"? i know the wont fit together, they sell adaptors.. OR should i just go 6" cooltube? is that size of a hood overkill? im ordering from a website where i can customize my package and its the same price for either or..