Are all bi-metal thermometers created equal? Not really. The problem with most bi-metal thermometers is that hang ups occur and you have to tap the thermometer to get an accurate reading. The cause of the problem is that the bimetallic helical coil in the stem of other bi-metal thermometers is tack welded to the stem itself. Our new line of thermometers feature a super sensitive bimetallic helical coil suspended from a copper coated bushing fixed in the stem. This superior design provides a faster response to temperature changes and assures more accurate readings. What does this mean? You don't have to tap the gauge with your finger as much. They are also accurate to 1% of the total range, feature a polished 3" 304 s/s housing, a hermetically sealed water proof case, glass face, external calibration capabilities, and a unique anti-parallax dial that provides for easy reading. The reading is actually taken from the last 2.5" of the probe. To calibrate properly the manufacturer recommends at 150F. The 3" probe takes longer to reach an accurate reading according to the manufacturer do to the stem being shorter. The range is dual scale, 20-240 fahrenheit and -20 to 120 degrees Celsius. The back connection is 1/2" MPT while the stem is 1/4" stainless steel. Manufactured by Tel-Tru. 8 year manufacturer's warranty. (1/16" Allen wrench needed to adjust temp) Calibration screw is 1/16th" hex nut.