Nature's Miracle Odor Control Litter Box Universal Charcoal Filters come in a 2 pack. These are made to fit most litter boxes with their Universal design and also include cutting templates for 15 top selling litter boxes. Nature's Miracle Odor Control Charcoal Filters naturally remove stubborn cat litter odor that is left behind in your cats litter box. These will help ensure your cats litter box smells fresh! *Each filter lasts up to 3 months Natures Miracle Odor Control Litter Box Universal Charcoal Filter - Liners & Bags