I have a question, my extractor is 125mm (220 to 2...

So, there are different sizes.. So, your tent is measured in m3. Hight,W,L Generally you want a filter to match your tent. A smaller one.. won't last as long.

Get the one that fits in the tent, with a higher CFM rating or m3/h so it puts less stress on the extractor and that fits the flange of your equipment. flanges are normally done in 2-4-6-8-10 inch sizes. I use a 4" flange on my stuff but I got a smaller tent. and my carbon filter is about double the CFM then my extractor. attaching any filter to your extractor will add a lot of resistence onto it and almost always lower the air flow rate by about 1/2