This thermos flask is made of a combination of Stainless Steel, Polypropylene and Silicone, and the dimensions are an excellent 21.1 x 12 x 9.1 cm. It is sized extraordinarily well for solo hikers who are concerned about size and weight but still wish to carry a hot brew around to warm up with. In our opinion this is one of the best thermos flasks on the market today. We’ve reviewed a selection of the best thermos flasks, ranging in size from 470ml to a whopping 64oz (1.8 litres). Bigger flasks usually retain heat better than smaller flasks, but are typically bulkier and heavier. We’ve compared their performance with our own temperature test. What Is The Best Thermos Flask? 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. Thermos flasks use an ingenious mechanism which consists of dual layers separated by a vacuum cavity between them. The vacuum is a region of space with no air or anything at all in it – this creates a natural barrier to heat leaving or entering the innermost chamber holding your drink. That’s why liquids in the flask remain hot or cold for longer than they would in a standard plastic bottle.

Heat Retention is a major factor determining the usefulness of a thermos flask. It directly affects how long your drinks or food will stay warm or cold. This flask from OKADI gets full marks for its capacity and versatility. OKADI is a brand that has been serving people with quality products for the last 20 years and this particular model is their flagship model. It’s a big flask for big groups Another advantage of stainless steel it that does not leave a metallic taste in the mouth or residual odours. However, it is always worth cleaning your flask thoroughly with hot soapy water between uses. You can see that a thermos flask will be a great companion for any outdoor activity! Using a Thermos Flask is Environmentally Friendly

Klean Kanteen TKPro 1L

As we said before, the Milu is more bowl-shaped and can easily be eaten from directly. The 6.6cm wide opening is extremely convenient for easy filling and eating as well. The Oneisall measures 34.5 x 11.5 x 11.5 cm and weighs 1.2kg. For a large capacity flask, those are not actually bad specifications. And it really does look the business! Beautiful lines as they say! Like almost any decent bit of outdoor kit, a good vacuum flask should also be robust and durable. All the flasks we tested are made of high-quality 18/8 food-grade stainless steel that resists dents, dings and scratches. The trade-off with steel flasks is that they can be heavy, although modern designs are shaving weight all the time, and in some cases, they now weigh little more than a standard plastic drinks bottle. If you’re after a large flask, the Oneisall 2L is a great stainless steel option with a lovely ergonomic design. This is a high-quality two litre flask which is capable of serving drinks for the whole family – great to bring along for day trips in the car or campervan.

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. Some thermos flasks use a cork or plug to seal the liquid in, but we really don’t feel this is an effective design. Our suggestion is to go with a screw cap and a clip-on outer cap which will double as a cup. Heat and cold retention is exemplary, with the Thermos lasting well over 24 hours for both. We found that it is particularly effective for cold drinks, with ice cubes still being solid after a 30 hour test we performed. Thermos have obviously squeezed out all routes for heat to get into the inner chamber of the flask.The GSI MicroLite 1000 Twist Water Bottle is a vacuum insulated stainless steel flask that has a one litre capacity but impressively small size and density. It is extremely lightweight at 0.37kg which is less than half the weight of the Stanley 18-8 for the same capacity. As we said before, vacuum insulation is important for keeping the heat energy inside your flask, and the Hydro Flask does this well. It is made of stainless steel that is extremely good for heat retention.

The flask has a BPA-free cup with enough space for several decent-sized cups of teas. The cup also helps ensure the flask remains leak proof. In terms of tech, the Oneisall employs a copper-coated layer outside of the vacuum space which ensures that the flask keeps your drinks hot without any heat reaching the outer surface. The Milu Thermo Food Flask is a bowl-shape flask (16 x 10 cm) that is not only useful for keeping your drinks hot/cold, but also certain types of liquid-based food. You can keep soup, rice, noodles, fruits and even baby food in this great flask. All parents know that it’s often a problem carrying baby food at the right temperature. The 450ml flask Milu is a great solution to the problem. Nothing beats a hot brew when you’re tramping around the hills on a winter hike. It’s like we’re hard-wired to appreciate that soothing warmth spreading around our bodies like a “Ready Brek” glow.The temperature performance of the Smardy is quite praiseworthy. It gives around 12 hours for hot drinks and 24 hours for cold drinks. Certainly good enough for day trips in any conditions. Flasks are more 'smell prone' than 'stain prone' – none of the flasks we tested had any staining after cleaning, but some retained a faint coffee smell.