Bacteriostatic water
Preserved, so the vial keeps for weeks refrigerated once broached. Sterile water has no preservative and is single use the moment you open it.
What bacteriostatic water is
Sterile water with 0.9% benzyl alcohol added as a preservative. The preservative is what makes the vial multi-dose: it suppresses bacterial growth after the stopper has been punctured, so the vial can be entered more than once within the period its instructions allow.
That is the entire difference between this and sterile water for injection, which has no preservative and is single use. Both are diluents, which is to say a vehicle rather than the active ingredient in anything. What may be supplied to whom, and on what conditions, is a question for a pharmacist rather than something this page should answer.
10mL or 30mL
Pick on how much you will use before the vial expires after first entry rather than on price per millilitre. A 30mL vial that gets discarded half used is more expensive than two 10mL vials that get finished.
The vial is glass with a rubber stopper and an aluminium crimp. Swab the stopper before every entry, and use a drawing-up needle rather than the needle you are injecting with, because coring the stopper blunts a needle fast.
Everything on the box, before you buy.
The incumbents make you register to see a price. The batch and the expiry you are shipped are the ones printed here.
Questions about bacteriostatic water
If yours is not here, the contact form routes to the person who can answer it.