Bo-Bottle is unique. This is the first glass drinking bottle with a screw-off bottom. All glass bottles are made with scratch-free Borosilicate glass, and are therefore very durable. The bottles are resistant to a lot, have a very long lifespan and stay beautiful. The cap and bottom are made of durable stainless steel. In addition, the inside is made of a toxic-free hard plastic, and highly resistant to bacterial growth.