The 20TH-320-4-M10 is a 2" Cylinder Head Temperature Swichgage for use on air-cooled engines. This model features a diaphragm-actuated, temperature-indicating gage, with a built-in electrical switch for tripping alarms and/or shutdown devices. This model has a 4 foot capillary length and a temperature range from 160-320°F (71-160°C). The sensing bulb on this model comes standard fitted with a 5/8-18 union nut. Included in the box is an Adapter Kit (10002450), M10 D or G Bulb with 10mm x 1.5 metric threading. The gage mechanism is enclosed in a steel case coated to resist corrosion. A polycarbonate, break-resistant lens and a polished, stainless steel bezel help protect this rugged, built-to-last instrument. This vapor actuated gage features a sealed capillary tube and a sensing bulb. When subjected to heat, the liquid in the sensing bulb changes to vapor creating pressure against the diaphragm mechanism. The diaphragm translates this vapor pressure into a mechanical gage reading. Inside the 20TH-320-4-M10, the gage pointer acts as a temperature indicator and as one switch pole which completes a circuit when it touches the adjustable limit contact. Contact(s) are grounded through the Swichgage case. This gage has a self-cleaning motion to enhance electrical continuity.