Honeywell CG511A1000 Medium Thermostat Guards Plastic Imported Clear plastic cover that resists yellowing Key lock with inner shelf to prevent tampering. Product Size (WxHxD): 6.06 x 5.06 x 2.63 inches Protects unwanted changes to AC/Heating preferred settings Fits the Honeywell thermostats below and other models measuring 6 Feet w x 5 Feet h x 1.75 Feet d or smaller:RTH8xxxx Family thermostats, RTH7xxxx Family thermostats, RTH6xxxx Family thermostats, RTH5xxxx Family thermostats, CT3x Family thermostats