New developed E-string with plain steelcore made of new material: the playability and the sound of E strings have been improved significantly so that the Wondertone Solo E has an outstanding sound volume and impressive power. Very often there is a metallic edge in other plain steel E strings' sound. In contrary, the Wondertone Solo E has a wonderful warm sound when playing pianissimo and is impressive brilliant in the higher registers. The string has a very fast response over the whole dynamic range and is also non-whistling.