First of its kind
I used to do a LOT of extraction tasks, while working as a Direct Support Machinist in the Army. I would have really-liked having access to this new type of extraction tool.
Old-style extractors needed "holes" to grip on a fastener to be removed.
This new set of extractors will grab on to existing heads, cut into them, and often remove them with no more than a wrench or socket.
As for dullness, the set has just about paid for itself in time and temper saved with its first or second use.
And, if you've got a rotary tool (Craftsman or Dremel) its possible to add some sharpness BACK into the bolt outs.
A GREAT tool to have. Sets come in several varieties.