The bulk of the cap is made from strong, 100% cotton twill material, with a sweat-resistant hem and reinforcing sewn around the inside. The brims are plastic (not cardboard), navy-coloured and embroidered with gold oak leaves and acorns. This is a symbol of high rank in the American navy, probably derived from the fact that the best ships were traditionally made from oak. The size-adjusting strap has a metal buckle, and metal sleeve for tucking away the end neatly. One size fits all.