The name of your air purifier, corresponding filter, Serial Number, and MAC addresses can be found labeled inside the fan part of your air purifier and in the Blueair app if you have a connected unit.
Check your product type on the air purifier's label:
• Turn the air purifier off and unplug.
• Carefully rotate the white top counterclockwise to unlock and remove it from the unit
• Check the fan cover for the product and filter information
Check your product type in the Blueair app:
• Open the Blueair app
• Select Product Settings
• Select Product Information 
Once you know your product type:
- You can go to https://www.blueair.com/us/air-purifier-filters
- Scroll down and select the model you have. All compatible filters and pre-filters will then be displayed.
- You can then click and order your filter as needed.
Alternatively, if you already know your serial number, you can go to https://www.blueair.com/us/contact-us-page.html and select “Help me find a replacement filter.” Enter your serial number, and compatible filters for your model will be shown to you.