Warchal developed this A string because some violins don't sound good with synthetic or gut strings; especially the response to high position playing on the A string. Many violinists therefore prefer a metal A string and Warchal developed the "Russian" style A string using the unique "Helix" design. The helix significantly improves the longitudinal elasticity of the metal core, with the result that the A string has a warmer and deeper sound, while maintaining high sound quality with a very good response. Click here for a video about the "Helix" design.
Click here for Warchal Avantgarde A string datasheet.