Made for your outdoor adventures, the Hydro Flask 591ml Wide Mouth Flask is crafted with professional-grade Stainless-Steel. The wider opening allows for faster fill and the TempShield™ double wall insulation keeps your liquids hot for up to 12 hours or ice-cold for up to 24 hours. So, no matter whether you’re on the top of a mountain or in the middle of the desert, you’ll be sorted!