Set / Baritone Ukulele 4-string d g b e' - Low D Tuning Wound D and G stringB/E strings made of SUPER NYLGUT, colour grey-black with mother-of-pearl shimmerAquila LAVA SERIES for ukulele - A grey-black string coloured with a touch of mother-of-pearl inspired by "volcanic rocks". Aquila's 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. The Lava Series strings maintain the same identical mechanical and sound properties of Aquila's famous white-pearl Supernylgut ukulele strings. Enjoy it!