✔12 PACK: Each set has 12 round compost bin filters charcoal, 7 inches in diameter and 0.5mm thick. Fits most compost bucket lids. ✔ACTIVATED CARBON MATERIAL: This compost bin filter is made of activated carbon, which is environmentally friendly and durable. It has a good adsorption effect and a longer service life. It needs to be replaced regularly. ✔GOOD ADSORPTION: The compost bin filter fits the compost bin to keep the odor down by adsorption and bring fresh air. It does an efficient job of eliminating odors from sink top compost pail and also prevents flies from entering and laying eggs. ✔CAN BE REUSED: Just rinse the filter out in a little warm soapy water to extend the life of the filter, make sure all the smell has gone. Do not use hot water as this caused filter to shrink. ✔CAN BE CUT: These compost bin filters are suitable for most kitchen compost bin sizes and are very soft, so you can trim them according to your own compost bin size.