Emerson G20 Universal Locking Thermostat Guard, Clear The product is easy to use and highly durable The product has easy handing Maximum thermostat dimensions that the guard box works with: 3 1/2" d x 5 3/8" h x 8 1/4" l. The maximum thermostat dimensions are 5-3/8 in. H x 8-1/4 in. L x 3-1/2 in. D, meaning that this guard box will not work with thermostats that are larger than the specified dimensions