Fenwal 01-017002-000 is a tube-like Thermoswitch Controller Thermostat with a cartridge-type head.  Small in size and can fit into a .625 in. (15.88 mm) reamed hole. 

The Thermoswitch operation principle is differential expansion between the outer shell and the inner strut assembly.  A great feature of the unit is it has an "anticipation" characteristic that minimizes the amount of overshooting and undershooting.  Also, it has a high sensitivity to temperature change and can control the temperature as low as -100°F (-73°C) and as high as 600°F. 

Properly installing the Thermoswitch will provide exceptional vibration resistance and performance.  Visit and download the installation instructions at the Technical Data tab.

The 01-017002-000 Model is UL Listed and certified by the Canadian Standards Association (CSA).