Under the category of small diameter tubes, we are offering ResMed SlimLine Mask Tube, ClimateLine Tube, and Slimline Tube. All these tubes are constructed by using flexible plastic and electrical components. The higher quality ClimateLine tube is used to increase the H5i Humidifier. This is done by the management of the air temperature, when it is passed via the tube. The tubes have a climate control system, which works automatically to adjust the temperature and keep it steady in the tube. All the small diameter tubes are ideal for keeping a comfortable humidity level.