This model is made by Western Humidors. This analog dial hygrometer is ideal for any humidor. Small and compact, it can fit practically anywhere. It reads relative humidity (RH) . Technical adjustments can be made at the rear of the hygrometer for easy calibrating. Plastic lens is concave and unit is fully housed in a brass case. This model easily attaches with magnet at back. Humidity sensors are on the sides of this hygrometer, so this unit should be mounted and used with the magnet or your own Velcro, and not inset into the side of a humidor.