Light bulb bottle charms. 20x10mm glass vials. Opening is approximately 3.5mm. Includes glass bottle, rubber stopper and silver-plated cap with 2.5mm loop. Size listed includes cap, which adds about 6mm to overall height. Use superglue to attach the cap. For oils and other liquids, use the stopper. If metal cap doesn't fit over the stopper's rim, snip edges of the stopper's rim with wire cutters.