Shoulder Rest SOLOIST Violin/Viola (S501) Fits full 4/4, 3/4 and most 1/2 size violins and violas. 3-Layer Design The Soloist shoulder rest offers 3 unique layers. 2 Layers have all of the features of the Concert Master model: One layer is made from special acoustical material, delivering enhanced sound, ultimate comfort and a secure hold. Another layer attaches simply with air to the back of your instrument using micro-air technology. The 3rd white layer is made of acoustical material of a different density and responsiveness and it allows the Soloist to created increased resonance and the maximum overtones that a Violin or Viola can produce. The 3rd layer combines with the first two layers to deliver added projection, more brilliant sound and added comfort.ALL AcoustaGrip Violn/Viola shoulder rests share the following features: Has no clamps that mute the violin's sound.Clamps stop the vibrations of wood. Increases the volume of sound and adds better quality with more overtones. Is very comfortable, ergonomically designed and stays attached with air. Gives a secure hold for the violinist or violist and attaches repeatedly on and off. Sticks without glue or clamps with no damage to the varnish, edges or back of your violin or viola. Fits easily inside the instrument case, resting over the bridge to keep your instrument securely in place. Protects your chin, neck and collarbone from sores and marks and alleviates the shoulder pain and restrictive movement of rigid, vice-gripping traditional shoulder rests.