With the tremendous popularity of the 40 oz and 64 oz industry standard Wide Mouth bottles, Hydro Flask decided to add another member to the Hydro Flask family - the 18 oz Wide Mouth! All of the same great features you have come to expect from the Wide Mouth now in a compact, easy to carry size! Hydro Flask water bottles were developed to perform in every environment. Each Hydro Flask is hand cast from double wall vacuum insulated food grade 18/8 stainless steel, therefore they are BPA-Free and resistant to bacteria and odors. The double wall vacuum insulation technology allows Hydro Flasks to keep contents hot and cold!