I use these to cut various sized holes in vehicle wall panels and floors for retro-fitting electrical cables for such things as amps, solar panels, generators, etc.  These are inexpensive and work well.  You pay for the price, however, because you've got to watch the temperature of these Neiko bits very carefully.  I've burnt one out - but once I did that, I watched the heat more carefully and I haven't had any trouble since.  Just let the thing cool off before you try that second hole, is all.