Automatic flow control valve that can be manually set for different flow rates. The valve adapts to changing line pressure to maintain a steady flow rate in the downstream piping (see "Principles of Operation") without automation (neither electricity nor an air supply is required). These are not recommended for use with viscous fluids, fluids with high specific gravities, or fluids that contain debris or suspended solids. Accurate to +/- 6% of desired flow rate, and can be adjusted without removing the valve from a line.