From Lorann Oil’s Website: “Designed to fit 1-ounce glass bottles only. The eyedropper is incorporated into a threaded cap which can be screwed onto the top of the bottle. All 1-ounce size LorAnn Flavoring Oils and Essential Oils are packaged in glass bottles. All 1-ounce size Fragrance Oils are packaged in plastic bottles.
Please note: Exposure to certain super-strength flavors and essential oils may cause the rubber to degrade. For this reason, we do not recommend long-term storage of the bottles with the dropper tops as the cap.”