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