... the formation to be drilled. Size Available: "Q" series: AQ, BQ, NQ, HQ, PQ/AQTK, BQTK, BQ3, NQ2, NQ3, NQTT, HQ3, HQTT, PQ3 ... . NQ & HQ impregnated diamond core bit 6mm & 12mm Casing & Casing shoe bit NQ2 & NQ3 double tube & triple tube core bit Surface-set diamond core bit LTK48 & LTK60 drill bits ...