LitterWorks Carbon Litter Box Odor Absorber (6-pack + velcro attachment), compatible with Scoopfree Litter Boxes, Forever Litter Trays, and LitterWorks Eco-Trays Absorbs odors in Scoopfree waste compartment Thick (5/8") pad provides high capacity odor absorption Attaches under the lid of the Scoopfree litter box with velcro Includes (2) 4" pieces of self-adhesive velcro for attachment Lasts 4-6 weeks