Available to suit 2” to 6 1/2” at working pressures up to 15,000 psi. reverse circulation drill string, used in the field of petroleum extraction technology, used for packer sealing, unpacking, bushing milling, pipe string rotation during drilling cement plugs and other operations, and liquid circulation during sand flushing, etc. It is mainly used for oil production, downhole operations and Used by the oil testing team. The upper part is connected to the water hose, and the lower part is connected to the oil pipe string.