Hydro Flask insulated bottle, 32 oz

What it is good at

• Holding temperature for hours because of the vacuum gap between the walls
• Staying dry outside, so it can share a bag with a jacket
• Taking a knock without cracking, unlike a thin plastic bottle

Check before you buy

• Capacity against how long you are out and whether you can refill
• Mouth width: wide for filling and ice, narrow for drinking while walking
• Whether caps and seals are sold as spares

Who it is not for

Anyone counting grams on a long hike, for whom a soft flask is the lighter answer.

An insulated bottle is two steel walls with the air pulled out between them. The vacuum gap is what holds the temperature and, just as usefully, what stops condensation forming on the outside when the contents are cold.

The mouth is the other decision. A wide opening is easy to fill and takes ice, and it also lets a lot of water out at once; a narrow one drinks more politely but needs a brush to clean properly.