D'Addario EJ99B strings are designed specifically for baritone ukuleles. The 4th string is a silver-plated copper wound on nylon complimented by a 1st, 2nd and 3rd strings utilizing our exclusive Pro-Arté' Carbon material. Pro-Arté Carbon Ukulele strings are designed for the perfect blend of tone and projection. These fluorocarbon sets are ideal for progressive ukulele players looking for a bright, modern sound and is optimized with standard DGBE tuning.