Masks were added to the Samurai armors to serve as a protection for the head and the face from cuttings.
There are 4 types of mask designs that came into general use in Japan: happuri (which covers the forehead and cheeks), hanbō (covers the lower face, from below the nose all the way to the chin), sōmen (covers the entire face) and the me-no-shita-men (covers the face from nose to chin). We can also classify those mask depending on their facial expressions, most of which derive from the theatre masks. Without going into all categories, we see mainly two models: ressei men, a fierce expression with mustaches, teeth on view and wrinkles all over, and ryubu men, with a "noble" and quiet expression.
The following samurai masks are currently for sale: