Medium Universal Thermostat Guard, Clear. Cover For Wall Thermostats To Protect Against Tampering, Damage and Unauthorized Adjustment Of Thermostat Settings. Unique Double-Wall Construction Provides Extra Measure Of Tamper-Resistance. For Use In Both New and Existing Applications. Tamper-Resistant Lock; Key Cannot Be Removed Unless In Locked Position. All Models Mount Vertically or Horizontally On Wall or Exposed Junction Box. Vents In Guard Base Allow Airflow For Optimum Thermostat Performance. Dimensions: Outside Height: 6-1/2", Width: 7-1/2", Depth: 2-15/16"; Inside Height: 5-1/16", Width: 6-1/16".