I think the 91 series is called chamfer chisel. I used to use it
on my Makita 401 trailcutting saw. It works great as long as
you don't rock or barbwire it out, which I seem to be pretty
good at. Once the top corner is folded over, you have to file too
far back into the strap to un-fubar it, it ends up in the trash.
Carlton N1C has been a far better "dirty work" chain for me,
but the 91VS is great for small, clean wood kind of work.