Stainless steel shelves include 200-watt heater and sensor probe. FreeZone Small Tray Dryers include three and can accommodate two additional Heated Shelves with Sensors. The Sensor, included with the Heated Shelf or sold separately, may be used to monitor sample or shelf temperature. Temperature is controlled and recorded by the required Lyo-Works OS. Useable space on each shelf is 10.6" w x 11.7" d.