They're made up of four layers:

1. The fine mesh layer catches any bugs, dust and other larger debris to extend the life of the main filter element.
2. The activated carbon layer removes most odors such as exhaust fumes, smoke and other noxious gases. For maximum effectiveness, use the recirculate option so that the air in the car is continuously scrubbed.
3. The filter media is an upgraded version of the factory filter and removes smaller particulates such as pollen, smoke and ash particles, airborne fungus etc. It's a HEPA-grade material, but, due to the limited surface area available in Model 3 & Y, the entire filter cannot be HEPA-certified, as it would need at least twice the surface area.
4. The final layer is made from aseptic cotton which provides a final deodorization and anti-bacterial treatment.

Please refer to the video for the installation procedure.