The modern design is not only interesting but deliberate. The open-air structure creates maximum surface area exposure and space for air flow to provide effective and efficient fragrance release. Dry fragrance technology: Unlike aerosols, they don't contain any propellants or acetone so they are cleaner and there's no sticky residue. Eco-Air refill's are part of Fresh Product's closed-loop recycling program and are 100% recyclable. Freshens for 30 days. No mess dry fragrance. Eco-Air refills release just the right amount of fragrance while reducing fragrance overload.