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! Our 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. Our double wall vacuum insulation technology allows Hydro Flasks to keep contents hot and cold!