Used in extension rod connection, its function is to transmit impact energy from the rock-drill piston, as well as rotation torque, into the drill string with no losses. It must withstand and transmit up to 6300 blows per minute from the piston continually, with great endurance and dependability. Such as Coulping R25,CoulpingR25/R32,CoulpingR28/T38,Coulping R32,Coulping T38, (1)   Size: R25,R28, R32, R35,R38, T38, T45, T51,R25-R28, R22-R25, R25-R32 R32-R38, R32-T38. (2)   Length: 140mm-235mm (3)   Package: in wooden case or in carton. (4)   Productivity: 5000pcs/ month