5ml cobalt glass vials are a “must have” for creating your own personal blends of essential oils for aromatherapy. These 5ml blue glass vials are perfect for testing out a small amount of a new blend, giving out samples, or taking your essential oils with you on the go. Undiluted essential oils should be stored in glass containers only. If a plastic container is used, the essential oils may cause the plastic to break down over time which can destroy the oil. Cobalt blue and amber glass bottles are preferred because they are able to block harmful UV lights which are damaging to the oils. The orifice reducer makes dispensing your essential oil easy, allowing only drop by drop of oil to come out of the bottle. This reduces the chances of spilling your precious oils. A 5ml (1/6oz) glass vial holds approximately 125 drops of oil, but will vary depending on the oil’s thickness.