German WWI M17 Steel Helmet with Leather Liner Copied from an original Stahlhelm M1917 in the IMA collection. The shell is comprised of 1.8mm thick steel. One of the most hefty and historically accurate M17s on the market. Genuine Leather Liner. Size fits US 7 (56cm) to 7 5/8 (61cm), adjusted with the easy removal of padding.