when the die is opened the inside high pressure of the finished product immediately breaks the wall part of the finished product which extends to the adjustment element 35 and escapes to the outside to let inside pressure and outside pressure be balanced when the aforesaid pin 32 is abutted against the pin of another cavity high pressure from extrusion passes along the groove 34 to break the wall part of the finished product which extends to the adjustment element 35 and to escape to the outside alternatively the aforesaid through hole 33 can be made at the surface of the cavity 31 at the desired location and the aforesaid adjustment element 35 can be installed in the through hole 33 and adjusted to control the wall thickness of the finished product in the through hole 33 so that when the die is open the inside high pressure of the finished product immediately breaks the wall part of the finished product which extends to the adjustment element 35 and escapes to the outside the let inside pressure and outside pressure be balanced referring to fig7 the extruding die 1 comprises a conical core 11 made subject to the design of the desired finished product an air nozzle 12 mounted in the conical core 11 a ring shaped mold plate 13 mounted around the conical core 11 and adjustment screws 14 controlled to adjust the gap between.