Like a traditional gouge, the reverse bent gouge chisels start with a flat profile, and go through to a deeper profile. The shaft is also bent, allowing the very unique profile and bevel of this chisel to be used in hard to reach spaces.
Number. 20 chisels have a very slight gouge profile to them, more so than the flat profile of the Number. 10's, with the profile doubling in depth with each increase in number, with the Number. 30 being the deepest.
Chisel Number. 25's and 28's feature deeper gouge profiles still.