Thermos Ultimate Flask Review (2024)

Are you in search of a flask that stands the test of time and keeps your hot drinks exactly that – hot? Look no further.

In this deep dive, we’ll explore the Thermos Ultimate Flask, a contender often touted for its ultimate durability and performance. This isn’t just another flask review; it’s an in-depth analysis of what makes the Thermos Ultimate Flask, in my opinion, the best flask for your outdoor adventures.

To see how the Thermos Ultimate compares, be sure to check out my detailed article on the best thermos flasks here.

Quick Overview

The Ultimate Flask, designed with adventure in mind, excels in keeping hot liquids warm and cold drinks chilled for up to 24 hours, thanks to its Thermos vacuum insulation technology. Constructed with a durable stainless steel interior and exterior, it’s robust yet comfortable to handle, staying cool with hot liquids and sweat-proof with cold. Its compact size and lightweight design make it an ideal companion for any adventure, further enhanced by protective silicone rings for extra durability and a two-part stopper for easy, spill-free pouring.

Thermos Ultimate Flask Features & Specs

In my quest to find the perfect flask, I’ve put the Thermos Ultimate Flask 500ml through rigorous testing. The insights shared in the following sections are based on my hands-on experience with this 500ml version. It’s worth noting that there is also a larger 900ml variant available, but the focus here will be on the more compact and versatile 500ml model.

Size & Weight

Whilst the 500ml version may not be a particularly big flask, the Thermos Ultimate Flask masterfully balances size, shape, and weight. At 300g, it’s light enough for easy transport yet robust in its construction. The 500ml version measures 6.7 x 7.2 x 23.6 cm, offering a sleek, compact design that defies the bulkiness of typical flasks.

This flask allows you to pour two regular-sized coffees, providing ample capacity without the cumbersome weight and size often seen in other flasks.

Price 

Priced at £30, the Thermos Ultimate Flask represents remarkable value, especially when considering the renowned quality associated with the Thermos brand. I personally think this price point is very reasonable, particularly in comparison to similar products from other top-tier brands. Although not the cheapest option, it’s still a cost-effective option for those seeking a good thermos flask without compromising on quality. For the most up-to-date prices and best deals, check out my top recommended retailers: Amazon, Decathlon

Insulation Technology

The core strength of the Thermos Ultimate Flask lies in its Thermos vacuum insulation technology, a key factor in achieving maximum temperature retention. This advanced technology ensures that a hot drink stays piping hot and cold drinks chilled for up to 24 hours, a testament to its superior heat retention capabilities. Remarkably, even with such high heat retention, Thermos’ advanced tech keeps the exterior cool to the touch.

There’s a reassuring certainty in filling up this flask in the evening before heading out for a wild camp, knowing, come morning, I can wake to a boiling hot cup of coffee, just as fresh and piping hot as when I first made it.

Protective Silicone Rings

A standout feature of the Thermos Ultimate Flask is its cold protective silicone rings. Unlike many steel flasks that are prone to dents and scratches from rigorous outdoor use, this flask is fortified with silicone rings for ultimate durability. These rings not only add an extra layer of protection against the elements but also enhance the flask’s grip, making it easier to handle in various conditions.

For the ultralight backpackers out there, the silicone rings can be removed to save almost 40g.

Two-Part Stopper

The Thermos Ultimate Flask features an innovative two-part stopper. This design includes two different stoppers: a screw-top that ensures a secure, leak-proof seal, and a secondary stopper that allows for a smooth flow when pouring. This combination makes it effortless to pour your drink without having to remove the entire lid, minimizing heat loss and spillage.

Cup

An often overlooked yet essential feature of a flask is its cup. Perfect for those lunch time breaks on the trail, the built-in cup provides a convenient way to grab yourself a quick tea or coffee on the go. When filled to the brim, it holds approximately 125ml, allowing you to savor 4-5 cups of your favorite hot drink from the flask’s lid. This means you can enjoy multiple servings of tea or coffee throughout your day, without the need to carry an additional travel mug.

Durability

Designed for the adventurer, the Thermos Ultimate Flask’s durability is a standout feature, ready to take on the toughest challenges. Its robust stainless steel body withstands the rigors of outdoor activities, while the added silicon rings offer an extra layer of protection against impacts and drops. This flask is built to endure, ensuring it maintains its functionality and appearance no matter the adventure.

Volume

The Thermos Ultimate Flask is available in two sizes, catering to different needs. The 500ml variant is perfect for short solo trips or to share a brew with a friend. For those who regularly travel with a partner, the larger 900ml flask is an ideal choice, offering sufficient capacity for two cups each. This flexibility in volume ensures that whether you’re on a solo venture or with a companion, there’s a flask size that perfectly suits your needs, keeping you hydrated and refreshed throughout your journey.

Stylish Design

Merging functionality with aesthetics, this good looking flask offers more than just utility. Its stainless steel construction gives it a sleek, modern look, suitable for any outdoor setting. Available in four distinct colours – Matte Black (my personal favourite), Desert, Charcoal, and Silver – allowing you to express your own unique style.

Guarantee

Thermos underscores its commitment to quality with a 5-year guarantee for this flask. This extended warranty period reflects the brand’s confidence in the durability and performance of its product. For adventurers, this means an assurance of reliability and longevity.

Thermos Ultimate Flask Pros and Cons

Pros

• Exceptional temperature retention hot or cold.
• Durable – Build for adventure.
• Lightweight and Portable at just 300g.
• Stylish Design.
• 5-Year Guarantee.

Cons

• The two-part stopper requires correct alignment for a smooth pour.
• Price point may be high for budget-conscious buyers.

My Experience with the Thermos Ultimate Flask

Every time I leave the house, my checklist is pretty straightforward – keys, phone, wallet, and, of course, my flask. It’s become such an essential part of my daily routine. For nearly two months now, the Thermos Ultimate Flask has been everywhere with me, and honestly, I can’t imagine my day without it, especially my coffee.

So far, I’ve only used it for hot drinks during Winter, and its performance has been incredible. I’m looking forward to seeing how it handles cold drinks come summertime, and I’ll definitely share an update on how that goes.

What really makes me a fan of this flask is its look – the matte black finish with the orange silicone band is just cool. It’s got this simple, no-nonsense vibe, but don’t let that fool you. Inside, it’s packed with Thermos’s top-notch insulation tech, keeping drinks hot or cold for up to 24 hours. This feature is a game-changer, especially for those long hikes or overnight camps when I just don’t fancy carrying the extra weight of a camping stove but still want the luxury of a hot drink.

As I’ve been taking this flask everywhere, I’ve really gotten to see how tough and handy it is. It’s not just good for holding my coffee; it’s been a dependable buddy on my trips, handling the knocks and bumps along the way without a fuss.

Thermos Ultimate Flask Alternatives

Now, let’s see how the Thermos Ultimate Flask compares with other top flasks in the market.

Stanley Classic Legendary Bottle 0.75L

The Stanley Classic Legendary Bottle, at £50, is robust with its stainless steel construction. It maintains hot or cold temperatures for 20 hours and ices for 4 days, weighs 598g, and measures 89x89x298 mm. Its features include a leakproof twist-and-pour stopper, an insulated lid that doubles as a cup, and it’s dishwasher safe. Notably, it comes with a “built for life” lifetime guarantee.

The Thermos Ultimate Flask, however, is lighter at 300g, enhancing its portability. It slightly outperforms in temperature retention with 24 hours for both hot and cold, and its protective silicone rings add to its durability. Priced lower, it offers better value. While the Stanley Classic bottle boasts a lifetime guarantee, the Thermos flask’s lighter weight, longer heat/cold retention, and affordability make it a more versatile choice for diverse outdoor activities.

Primus Trailbreak 0.5L

Priced at £33, the Primus Trailbreak Vacuum Bottle 0.5L is a strong competitor in the flask market. Its vacuum insulation and double-wall stainless steel design effectively keep drinks at the desired temperature. Unique features include a powder-coated surface for improved grip and a lid that doubles as a mug. The bottle’s tapered design is convenient for slipping into backpack pockets or car cup holders, and its wide mouth makes it easy to fill and clean.

The Thermos Ultimate Flask, while similarly sized, differentiates itself with its silicone rings for enhanced durability and a lighter weight. While the Primus Trailbreak has a slightly higher price and offers unique features like compatibility with water purifiers, the Thermos Ultimate Flask’s longer temperature retention time and lower price point again make it a more practical choice for regular outdoor use.

Klean Kanteen Insulated TKPro Flask 0.5L

The Klean Kanteen Insulated TKPro Flask 500ml brings a unique set of features to the table. It boasts a TK Closure™ internal thread design and Climate Lock™ double-wall vacuum insulation, ensuring both hot and cold beverages maintain their temperatures for extended periods (20 hours hot, 75 hours iced). Notably, it’s 100% plastic-free, utilizing stainless steel and silicone, with an electropolished interior to prevent flavour retention. A standout feature is its integrated double-wall stainless steel cup and a 360° pour-through cap, complemented by a chip-resistant Klean Coat™ finish.

While the Klean Kanteen TKPro offers these specialized features, the Thermos Ultimate Flask remains a strong contender with its comparable features and a more affordable price compared to the TKPro Flask priced at £38.

Take a look at our Best Thermos Flask round-up to compare how the Thermos Ultimate Flask compares against more top brands.

More Thermos Ultimate Flask Photos

Final Thoughts

The Thermos Ultimate Flask stands out for its blend of durability, temperature retention, and portability, offering great value insulated flask at a competitive price. Its practical design and proven performance make it a top choice for outdoor enthusiasts looking for a reliable flask to accompany them on their adventures.

Learn More

Like this review? Well, you’re in luck as I’ve got a bunch of other great resources for you to explore here…

• Wild Camping: The Complete Beginner’s Guide
• Best Tents For Wild Camping
• Best Hammocks + Best Bivvy Bags
• Best Camping Stoves
• Best Portable Camping Fire Pits
• Best Places for Wild Camping Wales, Scotland and The Lake District

I bought the Thermos Ultimate Flask with my own hard-earned cash to test and review. My review is independent of the supplier and reflects my own unbiased opinions. Some of the links on this page are affiliate links, which means I may receive a small commission if purchases are made through those links at no additional cost to you. You can read my affiliate disclosure in the privacy policy.