Surface set diamond core bits 1. Q Series: AQ,BQ,NQ,HQ,PQ 2. T2 Series: T2 ... wear at the leading edge of each segment,tungsten carbide inserts are fitted on each side of the waterway. This kind ... bits cannot be used in broken or loose formatioSize Available:Q Series: AQ,BQ,NQ,HQ,PQ/AQTK,BQTK,BQ3,NQ2 ...