Surface set diamond core bits 1. Q Series: AQ,BQ,NQ,HQ,PQ 2. T2 Series: T2 46,T2 56,T2 66,T2 76 Surface set diamond core bits can be ... used with any type of core barrels. By varying the diamond grade,size,quality,and ... matrix hardness and crown shapes,the users can satisfactorily drill and core hard and ...