Question about Xiaomi Mi Smart Air Purifier

This filter fits the Smart Air Purifier 4:
Xiaomi Mi Smart Air Purifier (1 x)

To order the right filter for your Xiaomi Smart Air Purifier, you should note the filter types from Xiaomi. There are three main types: the blue (Basic), the green (Advanced) and the purple (Antibacterial) filter. The blue filter is the standard type and contains an additional layer of activated carbon, but this is not sufficient to filter gases or odours effectively. The green filter is an improved version that contains more activated carbon and is more effective against formaldehyde and other chemical compounds. The purple filter has a larger layer of activated carbon and is particularly effective against harmful chemicals and bacteria.

As your model is not specified, I recommend choosing the green filter if you need better removal of odours and chemical compounds. For an antibacterial effect, the purple filter would be suitable.