Dry yeast is sterile, strain-pure, and highly capable of producing great beer. Because it is dried, the shelf life is often a year or more and it is much more tolerant of warm storage or shipping conditions than liquid yeast. Dry yeast is also packaged with nutrient reserves and is ready to directly pitch without a yeast starter. For high gravity fermentations, more than one pack of dry yeast should be used. Yeast starters are not optimal for dry yeast because they can use up the nutrient reserves of the yeast. The downside to dry yeast is that not all strains can survive the production process, so there are far fewer yeast strains available for beer brewing (there is an excellent selection of dry strains for wine and mead making, however).