I get asked this question a lot...Is this vial sterile? If its sealed, yes...if its, open, no. If you need to re-sterilize a vial, you have an option. If you only have one or two, you can swish them with alcohol. If its a whole case, then you will want to cook them collectively at 250 for 2-30 minutes...This will sterilize them. What I like to do is have my rubber stoppers ready in isopropyl alcohol so they slide into the tops easy...once the rubber is in, the aluminum cap can be set on and crimped down while the vial is still hot. You won't have to touch the glass while using the crimping tool.