The Keggle Brewing Weldless Thermometer has a 4-inch probe, making it ideal for use in your Boil Kettle or HLT . The 6-inch stem is recommended for Mash Tuns. These are to be installed in a kettle or keg only. Not intended for use with coolers. All metal parts are 100% stainless steel, and the gasket is a high-temp, food-grade material. Requires a 7/8" drill bit to install.