The Velocity Boiler Works (Crown) 960122 240C Flame Rollout Switch is a safety device designed for use in Crown boilers to prevent overheating and potential fire hazards. It monitors the burner area for excessive heat caused by flame rollout and automatically shuts down the boiler when unsafe conditions are detected. https://www.partshnc.com/960122-velocity-boiler-works-crown-240c-flame-rollout-switch