Today katanas are mainly made of carbon steel of different quality. But there are some swords made of zinc and aluminum alloys, which are able to resist some external forces and are only used for decoration or non-tameshigiri practice. To determine the quality of a katana it is enough to check its "resistance" (how much it bends when it is hit), "elasticity" (the ability of katana to return to its original shape), and the "endurance" of the blade after striking (how long it lasts).