Pack of Replacement Filter compatible with all AirPop Active Soft Shells. Set of 4 pieces. Up to 40 hrs cumulative use per filter. Multiple Layer Mask The soft-touch exterior made from durable pre-formed microfiber is skin-friendly and lightweight. The softshell is temperature, water and abrasion-resistant. Shaped to the unique dome design for ideal airflow and a balanced air circulation The replaceable insert filter blocks bacteria, dust & particulates with electrostatically charged, double TorayMicron nano-fiber core layers. The unique outer layer protects from airborne contaminants, with the inner layer providing a skin-friendly and hypoallergenic environment and leading filtration.