achisholm (asker) Mar 1, 2004:

ring pulls, seems only to be used for drinks. I don't know if you've seen these types of seals but they're very commonly used for sterile injectibles (i.v. drugs, preparations etc.) and also for shipping radioisotopes.The bottle has a rubber stopper inserted into it, and this is fixed in place with an aluminium ring surrounding the circumference of the bottle, with a notch in it. The notch extends to the top centre of the bottle where it ends in a flat circle. The circle can be deformed to break the seal and either left in place (if you want to remove the contents using a hypodermic syringe) or removed completely so as to remove the rubber stopper.