Article: The Neapolitan style has an almond-shaped body resembling a bowl, constructed from curved strips of wood. It usually has a bent sound table, canted in two planes with the design to take the tension of the 8 metal strings arranged in four courses. A hardwood fingerboard sits on top of or is flush with the sound table. Very old instruments may use wooden tuning pegs, while newer instruments tend to use geared metal tuners. The bridge is a movable length of hardwood. A pickguard is glued below the sound hole under the strings. European roundbacks commonly use a 13-inch scale instead of the 13.876 common on archtop Mandolins.

Question: What are the Neapolitan mandolin made of?
metal strings