Instructions for budget cabin air filter.
1. Go to hardware store and buy cut to fit 20x30x1 (or so) air filter.
2. Get the scissors from the kitchen drawer (or maybe not from that location).
3. Trace expensive filter.
4. Cut out new one.
5. Install.
6. Repeat steps 3-5 for other vehicles.
A dirty one probably after 6 months, 4000 miles.