application : . Thermometer bellows coupling bellows fuel level gauge valve copper bellows no sealing high pressure bellows   vacuum bellows sensor bellows vacuum switch
types of joints : 1, both ends are external joints WW type  

                 2, both ends are internal joints   NN type

                 3, one end is external joints , the other with bottom   WDtype  

                 4, both ends are side cut from the trough QdQd type