RUTLAND Magnetic Burn Indicator monitors the performance of your wood- or coal-burning stove. At a glance, you will see the potential for creosote build-up. Magnetically attaches to a vertical, single-wall pipe or on the cooktop surface of a wood or coal stove. Indicates overheating or a low-temperature creosote buildup hazard. Displays temperatures from 100ºF to 800ºF. The heat-sensitive face will darken in color when exposed to unsafe temperatures.