Trerice 91000 Series Self-Operating Temperature Regulators are the #1 choice of original equipment manufacturers, mechanical contractors and industrial process engineers. These regulators are ideal for temperature control of industrial equipment, tanks and process streams. The self-operating design provides reliable performance under the most extreme conditions without the need for an external power source. These regulators are available with 2-way and 3-way valves in sizes ranging from 1/8" reduced port to 6". Capillary systems and thermowells are available in a variety of materials.