1-API Surface-Set Diamond Bits/core bits 2-diomand core bit 3-impregnated tube bits 4-impregnated diomand drill bits Surface- ... diamond bits due to drilling equipment limitations.TSP core bits are set with Thermally Stable Polycrystalline cutters, ... costs to be much reduced.Size Available of core bits"Q" series:AQ,BQ,NQ,HQ,PQ ... ,BTW,NTW,NXD3,AX,NX,NXC,AXT,T6H,4 9/16,NWD4,412F,SK6L146,TT46,TB56,TS116 ...