"During the Great War the first true "Crusher" Schirmmützen appeared with soft leather visors and no cardboard backing of wire stiffeners in the tops. These field duty Schirmmützen can literally be rolled into a ball without damage. (...) This cap was worn by a doctor that would have acted as an army physician or surgeon and was manufactured with a leather visor and without the band cardboard stiffener or cap wire in the top, giving it a distinctive "floppy" look."

source:
http://www.kaisersbunker.com/ht/evolution.htm

DISCLAIMER:
there are 2 hats included the sets, because I simply couldn't decide. You can decide/vote which one's best.