The glass display area is about 5/8 of inch across (or 15mm). The glass is about 1/2″ thick when closed.
Reversible sterling silver round locket features a swiveling bail so the contents can be viewed from either side. The space inside the locket is about 2mm deep, about the thickness of a penny. This is deep enough for two photos back-to-back, maps, dried flowers, letters, hair, or sand – nothing more.
These are the same lockets I use for my reversible butterfly wing jewelry.
The locking mechanism is a small screw nut at the top that unscrews to open the locket.