This thermometer allows you to measure the temperature of your stove or stovepipe. This is important because it allows you to make sure the stove is running at the correct operating temperature. Too low a temperature and creosote deposits will build up. Too high and your stove will have a poor efficiency. It has a few ways to mount to the stove, it is magnetic so will attach to most parts of your stove. It also has a hole in the centre allowing numerous attachment options and can also be simply placed on the top of the stove. Please: note the magnet won't work with stainless steel flues and the magnet tends to become weaker over time if used at higher temperatures (all magnetics demagnetise at high temperatures). Please remove packaging before using on the stove. Size 2.5 inches (about 63mm across)