Shoulder rests are attached to the bottom of the violin to make the instrument comfortable to hold and play. If you do not already have one you will need one for your instrument. They adjust to fit a small range of sizes, so if you or your child is moving up into a bigger size they might need a new shoulder rest. Shoulder rests fit on both violins and violas, so do not worry if you picked a viola shoulder rest and you receive one that says violin. The smaller sizes are collapsible for storage and the 15-16.5" Viola is not. We have more shoulder rest options available in store.