Breathe new life into your home or office with the clean fragrances of Ambi Pur's Cotton Fresh 3volution system. This clever plug-in air freshener uses 3 different complementary scents, which alternate every 45 minutes to keep your surroundings smelling glorious. This refill contains three 20ml cartridges, which together will last up to 90 days, when used for 12 hours per day at the minimum setting.