Durable Glass Construction: The essential oil roller bottles are made of thick, corrosion-resistant glass that is smooth and durable. They are anti-shock and not easily susceptible to leaking, scratches or breaking. Protective Amber Glass: The amber glass bottles protect oils from UV rays and prevent quick evaporation. They do not break down when oils come into contact with stronger, more corrosive essential oils. Corrosion-Resistant Stainless Steel Roller Balls: The stainless steel roller balls are corrosion-resistant and provide a massaging effect when applied to the skin. They help skin absorb oils better and provide a unique sense of relaxation. Leakproof Design: The roller bottles have a leakproof design with built-in gaskets and a tight screw thread cap. They prevent any liquid leakage and are great for travel. Reusable and Portable: The set of 8 roller bottles are reusable and portable. They can be used to create a variety of essential oil blends for use on the go.