Honeywell TG512A1009 Thermostat Cover With Lock And Keys, Outside Dimensions 7-1/4" Height 9-3/4" Width 3-3/8" Depth Inside Dimensions 5-7/8" Height 8-3/8" Width Unique double-wall construction provides extra measure of tamper-resistance Used 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