Coupling sleeve for Extension Drill Rod connection.High quality of alloy steels and CNC machining guarantee our reliable and consistent quality control of coupling sleeves.when using rock drills with male shank adapters and a conventional drill rod, a coupling is required to join the adapter to the rod, ensuring the ends touch for efficient energy transmission. Coupling sleeves are also used to connect several rods to each other in the same way. Coupling sleeves have a middle stop to prevent over-threading on to the drill rod. Thread: R22, R25, R28, R32, R38, T38, T45, T51, Function: Coupling sleeve, Adapter Coupling Type: Full-bridge, Semi-bridge