Shoulder rests are used to help violinists hold up their violin. There are many varieties of shoulder rests available, and the selection of a shoulder rest is very personal. Questions to consider when choosing a shoulder rest are: does it help me hold up my violin? Is it comfortable?
Some violin players don't use shoulder rests, and others use round, cosmetic sponges - please note you'll need to purchase rubber bands separately if you buy a cosmetic sponge. To minimize neck abrasions, some violinists also find it helpful to use a chinrest cover or place a soft cloth or scarf over their chinrest.