Austin Air Pre-filter for HM400/HM450
A washable cotton pre-filter surrounds the main filter in the Austin Air HM400 or HM450. It gets the larger pieces of dust to prolong the life of the more expensive HEPA filter. It can be hand-washed but most users throw out the old one after a year and install a new one. To change filters, the unit is turned upside down, four screws removed, and the old filter pulled out. It is a fast and easy process.
This is the pre-filter for the HM400 and HM450 (also called the HM400 Plus) in both 110volt and 220volt models.
Listing on GSA Advantage - ClearFlite Part No. 8009