I had a stainless steel kitchen waste compost bin that had holes at the top to supposedly allow air to circulate🤷🏼♀️. You need to buy these charcoal sheets to fit the lid to filter odors while letting air through. Unfortunately, the fruit flies still find their way in and I often found the larvae in the filter 🤢 I needed something to plug the holes with and have everything washed. They fit perfectly and close tightly. So hopefully no more flies.