Thanks for your contact.Towards AirMic 4S Air Purifier, it is a type of air purifier with a 3 in 1 filter.
The ultra filter refers to its washable Pre-filter, which just like a thin mesh pre-installed on the outermost layer of the white pet-allergy filter to prevent those large particles.;and the duo filter is the remaining 2 in 1 filter, which is the medical degree H13 so that it has a good function of removing terrible odor, harmful gas and other small particles.
You can choose any one according to your needs.
