This Lochinvar Pressure Relief Valve is a safety device designed to control or limit the pressure in a system and prevent potential accidents due to overpressure. The valve has a 1.25-inch inlet/outlet size, which refers to the diameter of the pipe where the valve is installed. It is set to activate at 30 pounds per square inch (psi), meaning it will open and release pressure when the system's pressure exceeds this threshold. This specific model is crafted with high-quality materials for durability and optimal performance in various industrial applications.