Cardboard sleeve costs one star
I could easily tell how effective this filter was from Day 1. Putting one used filter in the sunlight to refresh it while the other is in use is great. BUT, any garbage bag filling up with organic matter eventually softens the cardboard sleeve for the filter. I wish the sleeve were made out of plastic, something impervious to moisture and odor. Otherwise the filter is positioned in the perfect spot beneath the lid and is highly effective in keeping odors down.