These extra filters come with two sets of dual charcoal filters for the .6 Gallon Stainless Steel Compost Pail. Each set includes a square filter and a round filter that fit inside the lid of the pail.Each set lasts approximately 3-6 months, so with each order you have up to a year"s worth of use. While composting isn"t typically a smelly process, these filters will neutralize any potential odors that may arise in the pail, so you can keep it right on the countertop without worrying about any smells.The round filter measures approximately 5.5 inches in diameter while the square filter is approximately 4 inches square. Each order includes 2 sets. Used on the Brushed Stainless Steel compost pail # 442099 - ASIN: B008MA16QC