Mainly recommended to hard porcelain with request on faster drilling speed, long life, fine edge, no clip for hand hold machine. Dry using, Life span is min double when in wet drilling. The connecting mostly in thread as M14, M16, or 5/8-11 etc., Sometime request for hexagon, but not so often. Segment can be 3+2, 5, 6+1mm variou high for variou budget request meeting.