help me pick a filter

I have a hydro farm 400cfm in my basket with a speed controller on amazon... now I just need to pick a carbon filter.

Small veg/flower closet... less than 200 cubic feet.

Suggestions on what I can get to complete my order on amazon would be greatly appreciated

Thanks

6 inch btw

most importent is that it fit the ventilation, both in size and when we talk about how many cfm it can handle, filter must ba able to handle the same or more, not less, tho with a speed control its not a deal breaker, if you etc. can save 50$ on the smaller one and it can handle 95% you could go for it and never run your vent on max, specially now as you said it for Veg, I never run my filter on in Veg. fist when they begin to stink (mostly in flowering, maybe late Veg) as there is`t any real need, ventilation run smoother and more effective with out the filter and filters also have a life time on roughly a year of running, so no need to "waste" it when there is`t any odor (worst thing for carbon filters is high humidity, can shorten there life by half if high, carbon attract the moister)