The material selected for these humidifier inserts, a urethane polymer, absorbs more than thirty times its weight in water, absorbs more quickly, and is better looking and longer lasting than the florist's foam used in many other units. These inserts are encased in ¾" deep, black anodized aluminum boxes with removable lids so that it will be possible for you to take them out for filling and washing, thereby eliminating the mess and drips associated with soaking the entire container. Magnets are included for mounting the humidifier, but we recommend attaching it directly to the humidor with a screw. The Nonpareil Humidifier is a great value for its price. We believe that you will be impressed by its quality and performance.