Exhaust system recommendation

I have a 1m x 1m x 2m high tent and use a 4" AC Infinity Cloudline fan with the digital control panel. The highest I have ever run it is half way (5) but normally level 3 is all that's needed and you can't even hear the fan run. But, I have a "lung room" where I control the temperature and humidity and use efficient LED lights so I do not need to do a large amount of cooling. The fan automatically adjusts itself depending on the temperature and humidity parameters I set. This lower level of airflow also makes it easier for the carbon filter to remove odors. If you don't have control of conditions outside the tent you may have to compensate with more airflow. If running HID or HPS lights you will need more airflow. If the temp and humidity outside the tent isn't much different than inside you will need more airflow. Keep in mind that if running a fan closer to maximum the carbon filter will have a harder time removing smells. There are commonly available plumbing fittings (rubber boot used on drain lines) that can easily adapt a 6" filter to work with a 4" fan if needed. You can also purchase fittings specially made to transition from one size to another. Many photos and websites show the filter and fan mounted inside the tent at the top. That takes a lot of precious tent space. I keep my filter and fan outside. I set the filter on the floor with the opening facing up. Then I use a rubber boot plumbing fitting to mount the fan on top. The I use plumbing drain pipe to make a "snorkel" to go up and into my tent. That way you don't loose any space inside your tent.

Oh, you can also get carbon filters with a flange that will allow you to attach an extractor easy (Can-Lite for example do one that attaches to a 100mm fan) but always best to secure it with some duct tape so you are only pulling air through the filter and not letting smell escape the tent.

Calculate you volume in sqm and then get an exhaust which will pull that volume of air every few minutes. Keep it fresh and helps with humidity and temperature. E.g. 2m3 tent with a 100m3 extractor

Buy bigger than what you figure you will need and get a fan controller to set it where you want for. Need more and you already got it... Cheers