2xThickened and : Our replacement filter is made of fiber activated carbon with millions of microscopic pores that increases high adsorption for better filtration performance. 2x thicker than your average filters, reduce unpleasant odor efficiently and continuously 8-Pack of Cat Filters: Litter box deodorizer filters provides 8 months of odor control, And we recommend changing the cat litter box filters fits litter robot carbon filters monthly Keep Home and Clean: Charcoal filters for cat litter box can effectively absorb odors, Activated carbon filters improve indoor air quality by absorbing the peculiar smell in the cat litter box Fit for Litter Robot Filter: The Cat litter filter only compatible with Litter Robot 4,Please check the model number before purchasing filter fit for litter robot 4 filter Easy to install: No tools required. No measuring or trimming Simply lift the lid of the litter box and swap filter fit for litter robot 4 carbon filters out