This is an Exo Terra Heating Top, size S. It's a device placed on top of a cage to insulate the air inside. Heating function confirmed. Size: 15.5cm x 10cm x 2.8cm No box or instruction manual included. I used to use it, but I don't plan to use it anymore, so I'm selling it. There may be some minor dirt or imperfections, so please refrain from purchasing if you are sensitive to such things. Thank you for looking.