Parker Pressure compensated with free reverse flow, controled flow in one direction. 

A pressure compensated flow control valve that regulates flow at a selected rate within 5% regardless of fluctuations in inlet and outlet flow. This valve can be used with a variety of fluids including water and oil applications. Series PCCM Pressure Compensated Flow Control Valve 1/4 NPTF Port Steel 3 gal/min Knob Adjustment