The image shows an earring back stopper, often referred to as a “bullet clutch” or “barrel earring back”.

These are used to secure earrings, particularly stud or post earrings, to prevent them from slipping off.

They are typically made of materials like silicone, brass, or other metals, sometimes with a silicone insert for a more secure fit.

Barrel earring backs are a common type of earring finding and are available in various sizes and finishes to match different earring styles.