Catit Airsift Dual Action Air Purifier Pad, 6 Pack – Two Media Filter to Keep Litter Box Odors at BayBrand: Catit Color: Magic Blue Features: Keep Smelling Fresh: Introducing the Catit Airsift Dual Action Odor Reducing Pad, your new ally in keeping nasty litter box odors at bay. It is quick and easy to install, and effective for a whole month Double Filter: Combines two cat friendly filter media: our powerful Catit Magic Blue ammonia buster and activated filter to effectively lock in unpleasant smells Usage: One Airsift filter pad lasts for 30 days