Product:Round drill rods Thread type:R25,R28,R32,R38,T38,T45,T51 Hex25,Hex28,Rd32,Rd38,Rd45,Rd51 Length:1000-3660mm BETOPPER ----Thread drill rodsThread drill rods are made by hollow drill steels, there are two shapes:round type and hexagonal type,This hollow hole are usually named flushing hole, used for transmitting water or air during drilling.And the threads can be used for connecting ...