As stated in the item description, you can hit a 9 mm thick H steel with a single shot. Tight frame attachment to thick steel material which rust hardly and it does not fly welding fire easily, wood material base attachment to thick steel material which required twice or three times trouble, etc. can be easily and safely done. I can not get out of this box to avoid confusion with other drill bits, the place where the square bit is No. 2 is sad.