D'Addario Pro-Arte 4/4 Size Cello D Strings are designed by for serious musicians who are looking for the sound and feel of gut and the consistency of a synthetic core string. Pro-Arte strings have a clear, soft, rich tone. A string is alum/perlon. D and G strings are silver/perlon. C string is tungsten-silver/perlon. G available with tungsten winding in 4/4 size. Available 4/4-1/8 size. Heavy and light gauge available in 4/4 size.