The lower three strings are 100% nylon, while the upper ones have nylon cores but are sheathed with thin steel wire, just like the all-metal ones. They're all easy to pluck and press against the fretboard. Except for the fret dividers and the keys, which have metal axes, cogs and baseplates, the rest of the instrument (head, neck and body) is made of plastic. This guitarlele is very light/portable, easy to play and has a surprisingly nice sound considering the inexpensive materials it's made of and the low price. Seems to be somewhat less vulnerable to water and shock damage than a wooden instrument. Overall, an excelent buy!