Bacteriostatic water, sterile measuring devices and the consumables that turn a lyophilised vial into a working solution.Bacteriostatic water is water for injection with benzyl alcohol added at around 0.9% as a preservative — that additive is what makes repeated withdrawals from one vial defensible, and it is also why the label carries a boxed warning against use in neonates. It carries no buffer and no tonicity agent, so it is a solvent rather than a vehicle.How much you add is a free choice, and it sets your working concentration. Our reconstitution calculator shows the trade-off: more water spreads the same mass over more volume and makes small draws easier to measure accurately.