China Manufacturer Factory Price R22 R25 R32 R35 T35 R38 T38 T45 T51 St58 Gt60 St68 Retrac Retract Threaded Button Drill BitThread button bitsThread connection: R25, R28, R32, R38, T38, T45, T51, ST58, GT60 and ST68.Carbide profile: Spherical, ballistic and parabolic.Bit Faces: flat, concave, convex