I needed to drill a broken 12mm hardened bolt in a tight space on my Honda Odyssey and bought these in the hopes they would really run out were cobalt steel and would not wander excessively without center punch. It was just what I needed; I was able to center and hold the drill in the center of the bolt despite the awkward position while the drill penetrated the hardened M10.x bolt I was so concerned about. That use alone made this purchase worthwhile and I now have a whole set to use when I need something more than the junk drill bits sold at our local hardware store.