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 ... waterway. This kind of bits cannot be used in broken or loose formatioSize Available:Q Series: AQ,BQ,NQ,HQ,PQ/AQTK,BQTK,BQ3,NQ2 ...