"Set It & Forget It" A Truly Fully Automated Humidifier: Unique sensor measures humidity and microprocessor controller operates a quite fan to circulate humidified air within the humidor to exact desired humidity to within 1% RH. Control unit powered from any wall AC outlet or Battery Operated. Fully Automatic Totally Unattended, Reliable Operation Virtually Maintenance-FreeAccurate Humidity Control with Built In HygrometerIntegral Humidity Indicator Low Water/Battery Indicator Humidifies up to 10 Cubic FeetSuitable for 50 Count Cigar Humidors and Up Refillable and/or Replacement Water Cartridges AvailableThere is no drilling necessary! The Cigar Oasis"s power cord is a paper-thin acrylic ribbon designed to fit snuggly through any humidor lid seal in the rear, out of sight.Difference Between Cigar Oasis XL and Cigar Oasis XL-Plus:The main differences between these great products is the available power options for each unit and the size of the distilled water cartridges. This makes it versatile for traveling or if the power goes out. The distilled water cartridge, although is 50 % smaller (than that of the XL-Plus) to accommodate the battery pack. The Cigar Oasis XL-Plus comes with a full-size cartridge which allows it to last twice as long before needing refill, however is powered only by a standard home or office AC outlet. Note, that both units are the same size. Also, the refill cartridge we sell can be used on both units, however, with the Cigar Oasis XL, only without the battery pack in place.