The Blue Pure 311i+ Max Allergen Block Filter 2-Pack is a set of two activated carbon filters designed for the 311i Max Air Purifier. These filters are specific to the 311i Max model and are compatible with it. The filters are dual-stage with an allergen block design, providing lifetime service by removing allergens from the air. The compact size makes them suitable for use in any room, offering a convenient solution for improving indoor air quality. Each filter has a filter life of 9 months, ensuring continuous efficiency in capturing contaminants.