Fully Automatic Battery or Outlet Powered Built-In Hygrometer Low Water/Battery Indicator Perfect for humidors that hold up to 300 Cigars (up to 4 cu ft) The unique Cigar Oasis XL is a small electronic humidifier that is fully automatic. Just plug it in using a paper thin power cord that fits between the hinges on the back of the humidor, or connect the optional battery pack and it’s ready to go. The integral hygrometer displays the humidity in the humidor and also is used to set the controls point which is factory set at 70% RH, but can be adjusted to your own personal taste. The unit comes with a refillable, replaceable water cartridge that will last up to one year before it needs water, depending on how often the humidor is opened. The Cigar Oasis XL has a built in system, which accurately monitors the humidity and uses a quiet fan to filter and circulate the air in the humidor eliminating musty odors so common in well-sealed humidors. Cigar Oasis XL is designed to always keep your cigars fresh.