Package Includes: 4 * HAC-504 humidifier filter. Made of durable materials it is perfectly compatible with Honeywell filters to ensure moisture output. Humidifivation Capacity: A humidifier diffuses moisture into the air to help with a good night s sleep. Especially when the air is dry or sick a humidifier in the home bedroom can help you and your family sleep better and ensure sleep quality. Blue Pre-Filter: HAC-504 adopts upgraded technology to add blue pre-filter layer which can effectively reduce large particles in the air honeycomb wicking filter can inhibit 99% particle growth on the filter and improve the air.