Designed to fit glass bottles only. The eyedropper is incorporated into a threaded cap which can be screwed onto the top of the bottle. Please note, these droppers do not fit most LorAnn products. Only the following products are packaged in a 4-ounce glass bottle: 4-ounce Super Strength Flavors: Cinnamon, Lemon, Wintergreen (natural), Wintergreen (art.), Orange, Peppermint, Clove, Spearmint, Anise, Lime, Sassafras, Key Lime, Tangerine, Nutmeg, Almond (art.), Almond (natural), Ginger, Teaberry, Grapefruit, Lemonade, Jalapeno, Citrus Blossom, and Menthol Eucalyptus. 4-ounce Almond Bakery Emulsion is packaged in a glass bottle (all other Bakery Emulsions are in plastic). All 4-ounce size Essential Oils are packaged in glass bottles. 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.