Optimized for Concert Ukuleles tuned to standard GCEA tuning- / Black precision rectified nylon ensuring that the roundness and dimension control of each string are unsurpassed / Preferred for their warm and long lasting tone / Concert Ukulele, Rectified Black Nylon, Non-Ball End / Made in the U.S.A. for the highest quality and performance / Environmentally friendly, corrosion resistant packaging for strings that are always fresh