High Efficiency Particulate Air filter is 99.9% efficient at removing particles as small as 0.3 micron. This Compatible HEPA filter is designed specifically for the Aerus Guardian Angel air unit. Enjoy clean and pure air in your home and office with this high quality Air Filter. Multi-Stage Filtration System with Activated Carbon Filter This is NOT made by Aerus. Made for Green Piece High-Efficiency Particulate Air filter is 99.9% efficient at removing particles as small as 0.3 microns. Multi-Stage Filtration System with Activated Carbon Filter