Thanks to STU-BSPP restrictors it is possible to adjust the oil flow passing through and control the speed of a hydraulic cylinder or motor. The adjustment is one direction, on the opposite side the flow is free. The valves do not have an integrated hydraulic compensator and the set flow is effected by the pressure drops accross the valve. The valves can be easly installed inline inside the hydraulic circuit through the two BPSS threads ports. Depending on the chosen size, the STU-BSPP valves can be installed inside circuits with max working pressure of 400 bar (5800 PSI) and flow up to 300 lpm (79.2 gpm) The external body is made by steel and it is protected from oxidation by zinc plating treatment. The inner components are made of steel, hardened and ground where necessary. The knobs are made of aluminium. Plastic knobs are available on demand, for applications where aluminium components are forbidden.