The same helmet with both M91 leather chinstrap mounted (left) and M91 brass chinscale mounted (right). Only Field Artillery, Cavalry, Train, and some Garde Pickelhaubes will accept M91chinscales.
On the left is a mounted Troops chinscales at 3 mm, in the center, a mounted Troops chinstrap at 3 mm, and on the right, a typical Foot troops chinstrap at 1.5 mm, although some can go up to almost 2 mm in thickness.