What we have now and have kept on hand for the last 8.5 yrs came as Kathy and Martha described. It is a vial that has sterile water in the top part and powder in the bottom with a stopper in between. You mix the two by pushing down as they described. As long as they remain separated by the stopper I think the shelf life is a few years. I check ours at least once a year and when it is within about 5-6 months of expiring, I send for a refill.