This is the glass reservoir accessory of Oscar Nebulisers.
Why do we need it?
1. when you inadvertently break the glassware.
2. you need extra glassware to hold different essential oils.
3. your glassware is too overly used and needs replacement.
It is important to realise that while pure essential oils are 100% natural (with no artificial chemical added), over time they are corrosive to plastics. You must not put essential oils in prolonged contact with anything made of plastics.
In some cases, potentially carcinogenic particles from harmful plastics may find their way into the essential oil, making them dangerous when diffused. Always use materials made from glass to store and diffuse essential oils.