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. 10 chisels are a flat profile, with the Number. 20 having a very slight gouge profile to it, which is doubled each time with the increase in number, with the Number. 30 being the deepest.
Chisel Number. 25's and 28's feature deeper gouge profiles still.