Austin Air HealthMate PermaFilt Pre-Filter is Austin Air original replacement filter.
Austin Air HealthMate PermaFilt Pre-Filter fits Austin Air larger series air purifiers including:

• Austin Air HealthMate HM400
• Austin Air Allergy Machine HM405
• Austin Air HealthMate Plus HM450
• Austin Air Pet Machine HM410
• Austin Air Bedroom Machine HM402
• Austin Air Immunity Machine HM444

Austin Air PermaFilt Pre-Filter is available in two colors:

• Black - for units in Black, Midnight Blue, Graphite colors
• White - for units in Sandstone, White, Graphite colors

The PermaFilt pre-filter traps large dust and dirt particles.
The PermaFilt pre-filter protects fine True HEPA filter from faster contamination and helps extend its lifetime.
The pre-filter can be vacuumed right through the metal mesh of the air purifier housing with a soft brush.
The pre-filter has to be replaced with new one when it gets very dirty or ruined.
The pre-filter's lifetime under normal residential conditions - up to 12 months.