Hydro Flask x Vortex Unbound Waterproof Cooler Backpack. Color: Charcoal Grey. Size: 15L. Used twice, in nearly perfect condition. Unique item, you wouldn’t find this in stores. Item is now discontinued by Hydro Flask. Works great, doesn’t leak. Perfect for carrying drinks with you anywhere, concerts in the park, water bottles for street fairs, having to hike in to a picnic spot. There’s so many places this would be great for, especially for families with kids or adults that need drinks or chilled medicine while enjoying the outdoors and needing to be hands free.