This pre-filter is for use with Seaira 1st Generation Watchdog 900 dehumidifiers. It attaches to the inlet end of the dehumidifier directly in front of the regular filter. The purpose of the pre-filter is to help remove particles from the air before they hit the main filter. The pre-filter can be vacuumed and is washable as well. A pre-filter is included with your Watchdog dehumidifier. This is a replacement pack.
The W915 comes in a 3 pack. Actual product may differ from photo.