Prometheus Optima Humidifier 100 CigarDesigned for a desktop humidor and Prometheus claims it is good for up to 100 cigars. Inside the plastic casing is a foam like material that has been chemically treated so the evaporation of water is controlled to be slow, gradual and at a constant 70 percent relative humidity. Set up is fairly straightforward: undo the packaging and pour distilled water onto the foam through slits in the plastic until it is saturated, then lay flat on a paper towel