The Gokujo ito are the considered to be the highest…
The Gokujo ito are the considered to be the highest quality string for shamisen, and ideal for stage use.
Note: The ichi no ito will not fit in a nagauta/jiuta shamisen, as the diameter of the string holes in the itomaki are smaller. It can be done if you widen the string hole first, but I've tried using such a thick string on a nagauta shamisen as an experiment, and feel that the tone of the thinner string balances much better with the smaller size of the nagauta shamisen.