Passive intake. Size matter?

So my Exhaust is a 170 cfm fan that is 5" what size should my intake (passive) be? I forgot if its supposed to be same or smaller or bigger. Lol

A general rule is 2-3 x as big exhaust. This is highly debated with many on here but from my experience it works.

thread closed. LoL; superstoner has it right. if you follow this guideline you should be golden, but if for some reason you arent content with the temps, simply add another passive intake hole. only con at this point with 4x In my experience is slight smell leak from circulation fan being stronger then my scrubber fan. i vent my cab separate from my light (two stage) but if you vent your cab and light with one fan on a filter you should be good.