The "CROWN" impregnated diamond core bits are the most commonly useful bits in mineral exploration, ... we can supply N, H, etc. The "CROWN" impregnated diamond core bits are the most commonly useful bits in the mineral ... the cost of diamond drilling to a minimum.Size Available:Q Series: A,B,N,H,P/ATK,BTK,B3,N2 ... ,NWD4,412F,SK6L146,TT46,TB56,TS116,CHD101All Chinese sizes Diamond Core Bit