What is your concern...dirt or bugs?
I have researched screen materials and found "BUGBED 123" to be the best all around. It is made by Green Thumb Group in Downers Grove, Il. It has the best insect exclusion with moderate airflow resistance. Sadly though, I have not been able to find it for sale yet on the net.
No-Thrips (Green-Tek, Edgerton, WI.) is also quite efficient but has a much higher air resistance. I have seen it for sale at Greenhouse suppliers.
If you are not worried about bugs you can use a regular window screen or aircon filter.