Robertshaw 720-051 Hot Surface Ignitor Gas Valve. The 720-051 is a genuine product manufactured by Robertshaw, who is a dedicated producer of home and commercial thermostats. This particular product is a Gas Valve that is used to replace constant pilot gas valves. The valve has four different gas flow positions including "set", "on", "off" and "pilot". Its included stops on the valve will prevent the valve from accidentally being switched to the off position. This valve is great when it comes to its flexibility with gas applications, and is usable with both propane and natural gas. It can also be mounted in any position, but should never be mounted upside down. The switch is on top of the valve which makes it easy to be maneuvered to a different position.