Soprano Ukulele Set GCEA - Regular Tuning, Key of C Made of SUPER NYLGUT Colour: grey-black with mother-of-pearl shimmer Aquila LAVA SERIES for ukulele - A grey-black string coloured with a touch of mother-of-pearl inspired by volcanic rocks. Aquilas Lava Series, naturally inspired by volcano, an hawaiian symbol of new life, is the respectful homage to the hawaiian people who made the ukulele worldwide famous and share their happiness with thousand of people all around the world.