Installing grow tent vents

[Personal Stash]

I saw an ad a while back for after-market vents that you can add to your grow tent. I want to add a 4" round vent to my MarsHydro 4'x2' tent. Does anybody know where these are sold or what they are called? Thanks.

 

[Phytoplankton]

Google is your friend, found several, "grow tent air filter vent" (on ETSY). They run about $9-$15.

 

[SmokingWings]

I want to add a 4" round vent to my MarsHydro 4'x2' tent.

Do you mean cutting a new hole in the tent fabric? Or, using an existing 8" or 6" round vent and stepping it down to 4 inches?

If you want to step down then all kinds of options available at or through any decent grow shop.