Odor control and filtration - The set includes round and square compost bin filters that absorb odors from composting bins, helping your kitchen stay smelling fresh and clean. The two shapes work better together for improved filtration. Easy to use - Simply push the replacement filters into the compost bin lid. Square filters also work in round lids because the rim will hold them up securely. Activated charcoal material - Made of activated charcoal for effective odor adsorption. Do not rinse; use as provided for best performance. Size and compatibility - Square filters side length: 4.75 inches. Round filters diameter: 6.75 inches. Compatible with most stainless steel compost pails. Can be cut into any shape to fit actual size. Use scenarios - Daily kitchen compost bin in a home to minimize smells. - Office or shared kitchen with stainless steel pails. - Lid size varies or nonstandard shapes? Trim or cut to fit as needed.