Waterproof Temperature Indicator with Stainless Steel Probe. The TM20 is a Compact Waterproof Temperature Indicator with Stainless Steel Probe. Includes 0.78" (20mm) stainless steel probe with 9.6ft (2.9m) cable. Measures temperature from -40°F to 158°F (-40°C to 70°C). Complete with foot stand, temperature sensor, and a CR2032 3V button battery. CE certified.