Surface set diamond core bits 1. Q Series: AQ,BQ,NQ,HQ,PQ 2. T2 ... : 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 ... fitted on each side of the waterway. This kind of bits cannot be used in broken or loose formatioSize Available:Q ...