FS/125 is part of the pneumatics system. It is a type of pneumatic valve that is used to regulate the flow of air, fluid, or vapor. It utilizes a mechanical diaphragm and valve mechanism to control the flow. It is designed with an integral pressure differential valve, which enables the control of pressure, flow rate, and direction. It can be used in a variety of applications, such as controlling air compressors pressure, controlling and regulating air flow, controlling air pressure in air-operated tools and equipment, and more.