Honeywell L641A Cylinder Thermostat The Honeywell L641A Cylinder Thermostat is designed for surface mounting on domestic hot water cylinders. It can be used to switch directly a wet central heating circulating pump or boiler, or to operate spring return and motor open/motor close zone valves. Key Features and Benefits: Honeywell Cylinder Thermostat Ideal for General Applications Suitable for Use on Uninsulated and Foam Lagged Cylinders Surface Mounted Double Insulated Fixing Strap Included Height: 77mm Width: 125mm Manufacturers 1 Year Guarantee