Simply take a pair of scissors and cut the 3 active carbon filters down to the required size for your own covered litter box and place them inside you should get about 9 12 replacement carbon filters to a pack for your covered litter box depending on the size of the filter once cut down filters that contain active carbon come in handy in plenty of ways for cleaning up air and gas the very large inner surface area of the active carbon absorbs nasty odours very effectively particularly orga