Cork stoppers are small, cylindrical pieces made from the bark of the cork oak tree. They are primarily used to seal bottles, especially for wine and spirits, to keep the contents fresh. The natural properties of cork make it an excellent material for this purpose, as it is lightweight, impermeable, and can expand to create a tight seal. These stoppers have been used for centuries and are valued for their ability to allow a small amount of air exchange, which can enhance the aging process of wine. Cork stoppers come in various sizes and shapes, catering to different bottle designs and uses.