The opening is approx 6mm and each bottle measures 40mm long x 10mm wide.
You have 12 empty glass vial bottles with plastic caps, they can be reused over and over again because the caps can be put on and taken off with ease. If you wish the cap to remain on forever simply place a small amount of superglue to the edge of the cap before plugging the bottle. The bottle is suitable for crystals, locks of hair and even liquids. Many people turn them into spell bottle pendants and add a little written spell, oil and herbs etc. The top does have a hole making it very easy to thread a thin cord or attach a chain.