Follow
Idk #RamseyCylinder sounds better. Rubber forms seal. Fan shrouds below. Also note some 4" inline fans and 6" (with reducer) can also attach.
https://www.etsy.com/listing/1064768181/set-of-3-140mmx140mm-4-inch-round-heat
Example of 4" "mixed flow" fan. These are commonly used in w/ indoor grow ventilation. Also note some Noctua fans have higher static pressure than ARCTIC P14s, performed better with this filter.