In an oil-flooded screw compressor, oil is injected into the compression cavities to aid sealing and provide cooling sink for the gas charge. The oil is separated from the discharge stream, then cooled, filtered and recycled. It is usual for some entrained compressor oil to carry over into the compressed gas stream. In some applications, this is rectified by coalescer/filter vessels. Within the compressor body there are two screws with matting profile: a female and a male screw, female having concave inlets and the male with convex helical inlets. The screws rotate in opposite directions with the female screw receiving the driving power and transmitting this power to the male screw through a set of synchronization gears of the screw compressor.