1-1/4" 3 way diverting valve. Proportional, non-electric mixing valve. With an increase of temperature at remote sensor The straight thru port opens, and the side Port closes proportionately. Install in the return line of a hydronic system with remote sensor attached to supply line to keep supply water temperature at a preset temperature. For systems between 17, 000 BTU and 200, 000 BTU. Valve, thermostatic head and remote bulb included. Capillary tube is 6' Long.