Sterile water for injection
Unpreserved. Use the whole ampoule or discard it, because there is nothing in it holding back growth.
Preservative free, single use
Water for injection with nothing added. No preservative, which means no benzyl alcohol, which means the ampoule is single use: once it is open there is nothing in it suppressing bacterial growth, so what is left over gets discarded rather than kept.
That is the difference between this and bacteriostatic water, and it is the only difference that matters. Which one you need is a question for your prescriber.
Plastic ampoule rather than glass
A plastic ampoule twists open rather than snapping, so there is no glass to break off and no filter needed to draw past shards. It is the safer format for anyone doing this at a kitchen bench rather than at a bench with a sharps bin under it.
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 sterile water for injection
If yours is not here, the contact form routes to the person who can answer it.