Factory Installed option to replace standard glycerol bottle(s) used for upper product temperature (and chart recorder, if applicable), with a solid temperature ballast specifically designed with the same temperature response as a glycerol bottle. Unlike glycerol bottles, which are susceptable to leaks or evaporation over time, solid ballasts are maintenance free. The solid ballast accomodates (3) 1/4" diameter temperature probes to aid validation and calibration activities.