The 750ml is the most popular size and is ideal for high school/tertiary students. It fits most cup and bike holders, and is the most common size with office workers.
Stainless steel has been used in the food and beverage industry for decades as it’s safe and doesn’t alter the flavour. And unlike aluminium it doesn’t require epoxy resin to be added, which we feel is the main benefit. Some studies also indicate that aluminium can contribute to Alzheimers.