We stock a broad line of insulators for use with all types and sizes of Thermocouple wire. Mullite ceramic insulators are recommended for use with base metal thermocouple wire and elements types E, J, K, N & T. High purity alumina oxide is recommended for use with noble or refractory thermocouple wire and elements, types B, C, D, S & R. Alumina is suitable for up to 3,600 degrees Fahrenheit. Mullite (60% AL2O3 / 39% SiO2) is suitable to 2,700 degrees Fahrenheit.