This dry-well is only four inches high and six inches wide, reaches temperatures as low as 10degrees Celsius, includes a NIST-traceable calibration, and is stable to plus or minus0.05degrees Celsius. The Model 9102S is excellent for dial gauges, digital thermometers, bulb switches, and other sensors that need calibration below ambient. It has two wells so you can use one for a reference thermometer to increase accuracy. Both wells are 1/2 inch in diameter, and each has inserts available for almost any sensor size. It also has a battery pack option that gives you approximately four hours of field use when AC power is unavailable. Block B has four holes that accept probe diameters of 3/8, 1/4, 3/16 and 1/8.