31x18mm with brass metal cap with loop. Note: the caps just fit (you'll definitely need to glue them on) or you can use another bead cap as a cap (see a couple options in photos and/or links below).
Fill with tiny beads or sand, or maybe a message in a bottle? Or a tiny paper flower? The inside diameter of the opening is 3mm.
Sold individually (actually a set of glass bulb and metal cap).