The thermocouple protection tubes illustrated on this catalog page are replacement tubes for Pyromation's complete ceramic protection tube thermocouple assemblies as found elsewhere in this catalog section, and they are compatible replacements for other manufacturers' protection tubes. The Series 16 mullite tubes are composed of 63% alumina, and have slightly more porosity than the Series 17 alumina tube composed of 99.7% alumina, which is considered to be more gas tight.