The Soloist violin/viola shoulder rests offer 3 unique layers of acoustical material, each of a different density and responsiveness. One layer is made from special acoustical material, delivering enhanced sound, ultimate comfort and a secure hold while protecting against bruising, sores and marks on your chin, neck and collarbone and relieving shoulder pain. Another layer attaches simply with air to the back of your instrument using micro-air technology. The White Layer gives the Soloist violin shoulder rest added projection, increased resonance and allows the musician to create the maximum overtones for the Violin or Viola. The Soloist's Ergonomic design sets the violin or viola's position at the most favored angle for ease of performance and the best sound projection. The Soloist uses no clamps or glues that would stop the wood's vibrations or damage the violin's finish. The 1697 'Napoleon' Stradivarius and the 1778 'DeLay' Guadagnini enjoyed AcoustaGrip for many years. Both instruments were acclaimed for their condition and set world record sales prices.