Inside BOP Valve is a kind of check valve with large pressure drop,tapered plug of valve,  reduces cutting action of the mud on the seat,to ensure that the correct closed position. Inside BOP Valve connected with drill string can protect swivel,hose and stand pipe.It also can be used before high pressure pump,prevent highpressure blowout.A dedicated release tool keeps the valve normally open and allows reverse flow to pass.This dedicated release tool pre-installed in the valve and the assembly prepared on the drilling platform,for quick installed on the drill string whenthe first signal appears from the well.