Hagen Catit Magic Blue Cartridge fits to all cats’ litter boxes, this includes reusable plastic holder and 2 filter pads This Hagen Catit Magic Blue Cartridge absorbs and retains up to 80% of ammonia and reduces fecal odors by an average of 40%, depending on your cat's cat food diet Safe and easy to use in any cat litter pan, the pads are also non-toxic and unscented Catit Magic Blue Cartridge also absorbs hazardous ammonia gases found in cat litter 25 times more effectively than carbon-based filters This cartridge is easy to disassemble and clean and it’s made of BPA-free materials that’s safe for your cats