This is the Alerton MS4-TH Ascent Microset 4 Temperature and Humidity Sensor. It is compatible with Alerton products and has a power source of 24v. The sensor is white in color and has a diameter of 1.243in. It is designed for use with the VAV-550 model. The item is new and sealed, with dimensions of 4.536in length, 3.040in width, and weighs 1 lb.