I have used numerous oasis for over 5 years. In my opinion it the best device on the market and is very affordable.

If you're really serious about keeping a constant %H then get one.

If you have a desktop, then the non-XL is fine. The XL is for a bigger cabinets.

However, I have an XL in my moderate sized Upmann desktop because I got a great price on it at overstock.com

It works perfectly.

The non-xl model as a thin film of plastic that drops over the cartridge holes when the fan is off. This prevents over-humidification due to abmient evaporation. If your desktop humidor is small skip the XL model.

Don't forget about the 1/2 cartridge that is also available.