Control litter box odors 24/7 with Arm & Hammer's Purrifying Pak. Utilizing the power of baking soda, this small, but powerful Purrifying Pak comes with 3 baking soda Fresh Scent paks that provides continuous litter box odor protection for up to 90 days! Designed with a universal fit, Arm & Hammer Purrifying Paks can be used on any litter box. For open litter boxes, the "cat tail" hangs from the rim of the litter box. For hooded or top entry litter boxes, an adhesive strip on the back of the Purrifying Pak sticks to the inside of your cat's litter box. For continuous litter box odor protection, count on Arm & Hammer's Purrifying Pak. PRODUCT TIP: Each pack comes individually sealed and is scented Fresh Scent. Replace every 30 days or as needed. If your cat aggressively kicks their litter after using the restroom, you can place the Purrifying Pak on the outside of the litter box and still provide odor protection.