Prefilter designed for Wood's Airmaster ozone generators, compatible with models WOZ 400, WOZ 500, WOZ 2000, WOZ 4000, WOZ 3000, and WOZ 6000. This pack includes 3 filters to protect the ozone unit, promoting efficient ozone production and extending its lifespan. Replace the prefilter as needed, typically every 6-12 months.