A roller bottle is used to dilute essential oils with a carrier oil (like fractionated coconut oil) and apply the oil/essential-oil blend topically to skin. Roller bottles have three parts:
bottle – The bottle is made of glass and can be clear, amber, or in a wide range of rainbow colors. Using amber and UV-coated colored glass bottles is often preferable because essential oils degrade in sunlight. Even with a UV coating though, it’s best to store roller bottles in a cool, dark spot to help them last as long as possible.
rollerball– Rollerballs can be made of glass, metal, or plastic. They nest inside of a plastic casing that snaps into the bottle. The glass/plastic/metal ball rotates around and gets coated in the oil/essential-oil blend and applies that mixture to the skin.
cap– twists on over the rollerball.