What material is used to make the bottles?
The glass bottle is made of a specific type of glass called borosilicate. It is specifically designed for thermal expansion so it will not crack during drastic temperature changes.
The plastic bottle is made of a material called Tritan®. It is a medical-grade, premium plastic, free of BPA (Bisphenol A), BPS (Bisphenol S), and EA (estrogenic activity).
You can read more about Tritan plastic on their website.
We use a food-grade 18-8 steel to make our insulated bottles. This grade of steel is non-magnetic and extremely resistant to corrosion.