Key attributes: Very light, design enables one-handed drinking, wide mouth for easy filling and cleaning. None of the flasks leaked from the main body – however, some flasks can't be filled to their stated capacity without liquid coming out when you screw on the lid. Capacity: Bigger capacity means more contents to enjoy. It also means more weight to carry, but only if you fill it to the brim. For best insulation, buy a flask that’s slightly bigger (but not heavier) than you need, and leave a couple of centimetres of air at the top. We’ve included capacity and weight info for all our flasks below. Since the American manufacturer, Thermos, came to fame, the term has become slang for vacuum-insulated flasks. Although the terms are largely interchangeable, the original scientific phrasing is 'vacuum flask'.

Capacity: 600ml (20.3oz) / Temperature test: 0 hrs 90°c, 90 mins 79.6°c, 4 hrs 66.5°c, 6 hrs 58.3°c, 8 hrs 51.6°c, 24 hrs 22.2°c / Stainless steel construction / Wide mouth opening / Other useful design features to look for include a wide mouth, which makes for easier cleaning and filling (especially if you want to add ice cubes to your flask). In addition, many larger flasks incorporate ‘twist and pour’ spouts, so you can pour from the flask without having to completely remove the stopper. An integrated cup is also useful. Smaller flasks often feature lid designs that allow on-the-go swigging or one-handed operation. Capacity: 1 litre (33oz) / Temperature test: 0 hrs 90°c, 90 mins 85.5°c, 4 hrs 79.1°c, 6 hrs 74.3°c, 8 hrs 69.9°c, 24 hrs 44.5°c / Made of food grade 18/8 stainless steel that doesn’t impart or retain flavour / Lid doubles as a mug ensuring you always have a cup handy / Silicon sleeve / Drinking stopper opens and closes with a slight turn / Additional standard stopper for optimum heat retention included / Tapered design for easier handling / Large mouth opening is easy to fill and clean. BUY NOW: PRIMUSEQUIPMENT.COMBUILT FOR LIFE: ‘Built for life’ is a motto Stanley stood by since 1913 with their promise to provide rugged, capable gear, built to last a lifetime; If your Stanley doesn't life up its legendary reputation we'll do what it takes to make it right It’s 100% leak proof – no matter how hard we tried, we couldn’t get any liquid to escape and the automatic opening trigger means you can drink from it one-handed with ease. Finally, there’s an additional loop handle on top so it can easily be attached to bags or simply carried this way. All in all, this is brilliantly stylish and robust

Capacity: 1 litre (33.8oz) / Temperature test: 0 hrs 90°c, 90 mins 86.5°c, 4 hrs 81.6°c, 6 hrs 78.1°c, 8 hrs 74.7°c, 24 hrs 53.7°c / Plastic-free stainless steel and silicone construction / 18/8 food-grade stainless steel interior doesn’t retain or impart flavours / Integrated double-wall construction cup / Twist and pour cap with 360° pour-through design / Internal Thread Design for increased thermal performance / Durable Klean Coat finish. BUY NOW: KLEANKANTEEN.CO.UK EXTREMELY DURABLE: Our leak-proof thermos bottle has withstood speeding bullets, 4000 ft drops and category 5 hurricanes; The iconic style and rugged durability of this insulated bottle means it’s made to go anywhere Key attributes: Leakproof, practical design enables one-handed drinking, wide mouth for easy filling and cleaning HOT OR COLD FOR 24 HOURS: Fill the 1L thermal flask with water, coffee, tea or other drinks, whether you're at home, work or outdoors; The double-wall vacuum insulation of this thermos keeps all your drinks hot/cold for 24 hours and 120 hours with ice We hand-washed each flask with hot soapy water and let them air dry overnight, then ranked them on smell.When single-use plastics started getting a bad rap, S’well became the drinks bottle of choice for a host of celebrities and ‘influencers’. But they’re not all style over substance – the design consists of a triple-walled construction incorporating a copper layer for improved insulation. This flask is lightweight and practical – the ergonomic shape makes it easy to hold, the really wide mouth makes for easy drinking, filling and cleaning, and the grooved lid makes it easy to open, even if screwed on tightly. It’s sure to draw admiring glances if you leave it on your desk at the office. It’s just a shame that the capacity is a bit small, and it’s relatively expensive for a little flask. Full Specifications