These 5/8 dram sample glass roll on bottles (vials) are great for sharing your favorite essential oils， are designed to easily apply your oils or blends， and are great for travel， for emergency or for personal use. Each mini roller vial will hold between 30-40 drops of essential oils. These 5/8 Dram (2 ml) sample rollers come with plastic roller balls and a black screw on cap. After you have added your oils to the bottle， make sure to press firmly on the roller as this will help avoid leaking. Thanks for looking!