We are proud to introduce the Bionylon ukulele string series, the first eco-friendly synthetic string in the world.These Ukulele strings are made of rounded, smooth Bionylon monofilaments... a new material discovered by Aquila that also boasts excellent acoustic and mechanical properties.Bionylon is 68%, a plant derivate (castor oil); this allows a reduction of more of 50% of carbon dioxide emissions in the atmosphere during the polymer-synthesis than the other common Nylons employed for musical strings.Warm and mellow perfomances!