Replacement water cartridge for the Cigar Oasis Excel that comes with battery pack for wireless/portable operation. This is the short style water cartridge that comes when you purchase the original unit. Also available is a full size water cartridge not intended for use with batteries. Clips on to the control unit and contains a foam element with the distilled water and antifungal agent. The fan in the Control Unit draws air from inside the humidor and passes the air through the foam which is full of water and the air picks up humidity and delivers it to the cigars in the humidor. Water consumption depends on the size of the humidor, how good the humidor seal is and how dry are the cigars when you put them in the humidor. Typically, for a well-sealed humidor of 75-125 cigars that is opened 3-5 times a week, the water cartridge could last as long as 9 to 12 months.