As the price of an impregnated core bit increases from a 6 mm impregnation depth through to a 16 mm impregnation depth, consideration should be given to the economics of selecting a particular impregnation depth. While the initial cost of a core bit with a 6 mm depth of impregnation is relatively low, the expected overall bit life will also be lower than that of a bit with a thicker impregnation depth. For this reason, a 6 mm impregnation depth is generally recommended for use in shallow drill holes or for non-wireline applications where more frequent bit changes are not objectionable. Conversely, the higher initial cost of a core bit with a 12 mm impregnation depth is largely offset by its inherently long bit life when used to drill extremely deep holes. The cost saving benefit is realized through reduced down time on the drill rig that would otherwise be required for tripping the drill string for bit changes.