... ,Our impregnated bits are manufactured to give optimum penetration rates and bit life, which is required to keep the cost of ... minimum. The optimum diamond size, concentration and matrix type are dependent on the hardness and abrasiveness of the formation to be drilled ... 9/16, NWD4, 412F, SK6L146, TT46, TB56, TS116, CHD101 Other sizes are upon clients' requirement.