After struggling to drill through some 3" aluminum forgings, but my normally reliable bits out of the box, was I am infinitely disappointed. bought, and what a difference! The jobber bits I normally use are probably fine for my usual thinner metals (no more than ΒΌ inch), but they made a world of difference on heavier applications. When I resharpened the cheaper bits by the 3" hole (literally), they weren't dull enough to be noticed.