This is a well made set of hole saws.  I have used them for a variety of wooden doors, piping runs inside walls, and one metal door.  In all cases the saws performed well.  I am not sure how well they would hold up to extended use on metal, however for my moderate useage on wood, and limited use on metal they have seemed to hold their edge quite well.  I originally bought a single lenox hole saw in a large diameter and had a cheap set of small diameter saws.  I picked up this set from amazon on some special and will never use the cheap ones again, even for small diameter holes.  I would have saved myself significant time and furstration if I had just purchased the "good" set at the regular price rather than trying to save a few dollars by buying cheaper versions of the small diameter saws.