Made to measure: hook-and-loop or roll
1. Layer structure
What holds back dust is the filter layer inside the product. A single layer of tightly woven mesh and a membrane with a nanofiber layer in the middle do not do the same job. Check what the filter layer is in the product description. How does it work?
2. Airflow
The tighter the filter, the more slowly air passes through. A good window filter should hold back dust while staying breathable. Ask the seller what airflow to expect on still days.
3. Washability
A window filter fills with dust over time. A product that can be cleaned with water lasts for many years; one that cannot be cleaned has to be replaced.
4. Fraying edges
If you are buying it by the roll and cutting it yourself, make sure the cut edges do not fray. Membranes whose layers are permanently bonded keep their shape after cutting.
