These Austin air purifier filters, austin air purifier replacement filters, and accessories are made specifically for our Austin Air air purifier collection. If your model was made or bought before 1995, you will need to purchase the HEGA HM405 filter for your unit. Otherwise you can purchase the filter configuration you like. All filter packs include a pre filter, hepa filter, and activated charcoal filter. The prefilters are available separately as an option if you care to change more than every 5 years with the mfg recommended filter change schedule.