Honeywell Medium Thermostat Guard with Inner Shelf to Prevent Tampering Plastic Imported Clear plastic cover that resists yellowing Includes universal key and heavy duty lock. Key lock with inner shelf to prevent tampering. Product size: WxHxD: 6.5 x 7.5 x 2.93 inches Protects unwanted changes to AC/Heating preferred settings Product dims: 6.5H x 7.5W x 3 D inches; .8 lb, interior dims: 5H x 6W x 2.75D inches. Does not fit all thermostats Installation is nearly effortless The Guard will fit on all medium sized 6W x 5H x 1.75D inches or smaller