... quality 3. Known for their reliability and logerity. PRODRILL thread button bitsRope thread:R32, R33, R38, R35T thread: T38, ... T45, T51, ST58, T60 GT 60. Main button bits diameters: R32-45MM, R32-51, R32-64, R32-76 ... T45-102MM,T51-89MM, T51-102MM, T51-127 etc. Button bit face design: Flat face, drop centre, Normal and Retrac ... with soft, medium, hard rock formation. . Retarc Thread Button Bit