Primus TrailBreak EX Flask Review

With its double-walled stainless steel body, the new TrailBreak EX Vacuum Bottle from Primus is a sturdy and effective flask. It comes in a choice of sizes - either .75 litre (at £35) or 1 litre (£40); in order to save weight and pack space, I went for the former. The TrailBreak boasts a couple of features that make it winter mountain friendly; however it is also fairly heavy.

Good weather for flasks  © Dan Bailey
Good weather for flasks
© Dan Bailey

Most immediately obvious is the silicone sleeve, which helps shield the flask body, adds a measure of extra insulation, and perhaps most importantly protects your hands from contact with exposed metal in sub zero conditions. The sleeve comes in a choice of different colours, and if you're saving weight it is easily removed. However, re-fitting it is a bit like trying to roll a condom onto a marrow (I imagine) and having once managed to wrestle it back on I've decided to leave it permanently in place.

The wide mouth of the bottle is easy to fill without spilling scalding liquid everywhere - a particular consideration in a tent, as Primus suggest. When it comes to cleaning, it makes things easier too. The double-walled steel cup holds the heat reasonably well, and has a plastic outer shell which again saves the hands from contact with cold metal.

It's pretty heavy for winter climbers  © Dan Bailey
It's pretty heavy for winter climbers
© Dan Bailey

...but it's hard to begrudge a hot drink on a cold day  © Dan Bailey
...but it's hard to begrudge a hot drink on a cold day
© Dan Bailey

The TrailBreak EX Vacuum Bottle is sold with two different stoppers. The conventional lid is a little lighter and seems marginally better for keeping things hot; alternatively, use the 'ClickClose' stopper when you want to be able to pour out the contents without having to completely remove the lid. The spout of this top is designed not just for smooth pouring, which it does well; it also fits in your mouth so that you can drink straight from the flask without dribbling juice down your chin. This is an obvious advantage when it's blowing a hoolie, though with still-hot contents you do have to be careful not to burn your lips. For ease of cleaning the ClickClose stopper mechanism can be disassembled.

The 'ClickClose' stopper pours smoothly, and you can drink from it too  © Dan Bailey
The 'ClickClose' stopper pours smoothly, and you can drink from it too
© Dan Bailey

"You can drink straight from the spout without dribbling juice down your chin"


Having used it on a number of cold winter mountain days in recent weeks, I've found it keeps water or squash very hot for several hours (I've not tried it with coffee, choc or soup as I'm wary of tainting flasks, though I'd assume the type of drink is unlikely to affect the rate of heat loss. Anyone?).

For a day of winter climbing in the Cairngorms, for instance, I filled it with hot squash at 05:30 before leaving home. The flask then sat in my pack for a few hours of driving and walking in, and was good for a lip-scalding drink when gearing up. At the top of the route at around 13:30, eight hours in, we finished off the contents - they were still warm, albeit no longer piping.

After eight hours the contents are still pretty warm  © Dan Bailey
After eight hours the contents are still pretty warm
© Dan Bailey

To be a little more systematic I tested it at home. First filling the flask with water not long off the boil, I then left it outside on a chilly day at about about 0C.

  • 0 hrs: 95C
  • 1hr: 92C
  • 2 hrs: 87C
  • 3 hrs: 82C
  • 4 hrs: 77C
  • 5 hrs: 74C
  • 6 hrs: 71C
  • 7 hrs: 66C
  • 8 hrs: 62C
  • 9 hrs: 59C
  • 18hrs: 42C

Cup, ClickClose stopper and conventional stopper   © UKC Gear
Cup, ClickClose stopper and conventional stopper
© UKC Gear

When I went to bed, at 9 hrs, the contents still felt genuinely hot. Even next morning at 18 hrs, after a frosty night outdoors, the water was lukewarm. There are two things to bear in mind here of course. Firstly, opening it every hour to check the temperature is going to make it lose heat faster (physicists have called this the observer effect, though they probably weren't thinking about anything as important as flasks). In addition, if you're carrying the flask in a rucksack rather than sitting it on a cold patio, you can imagine the heat retention being better.

In short, the TrailBreak EX performs as well as you'd hope of a well-made vacuum flask from a respected brand.


So far, so good. But there is one downer - the weight. Empty, the .75L model weighs a not-unappreciable 673g (my measure: Primus say 680g), while the 1L version is listed as 742g. By stripping the silicone sleeve, leaving off the cup/lid, and simply drinking from the ClickClose stopper instead, you can reduce the weight of the .75L flask to a minimum of 433g. However without the protection of the cup there's nothing to prevent the stopper opening by mistake in your pack. A more practical weight-saving option - doing away with the sleeve, and using the simple stopper and cup - weighs in at 510g. For family walks or even one-day winter hillwalking I would be happy to live with this, but for backpacking or climbing, when every gram counts, I'd find it hard to justify. Yes a hot drink is nice... but is it nice enough? If you do want a climbing flask, there are lighter alternatives: To take just one comparison, the Thermos Ultimate .9L flask is listed as weighing 380g.


It is robust, it performs well, and we like the fact that you can drink straight from the flask. However, it has to be said that the TrailBreak EX is pretty heavy. For general outdoor use, the car, cragging, casual country rambles and even - to an extent - snowy fells and munro walks, this is not by any means a show stopper; but it'd be a hefty load for winter climbers or overnight backpackers.

Primus say:

Primus' new TrailBreak EX Vacuum Bottles not only feature a rugged double-wall stainless-steel body, but also a double-wall stainless-steel cup, which keeps drinks hot or cold much longer.

A silicone sleeve improves the grip and prevents cold fingers (or possibly frostbite) in case you would touch the steel in very cold conditions. Of course it also offers protection to the bottle.

Coming with two stoppers, you can choose what suits your needs best: Use the regular stopper when maximum temperature retention is more important than the convenience of being able to drink directly from the bottle, as with the ClickClose stopper.

  • Material: Stainless steel with powder coating and silicone sleeve
  • Sizes: 0.75L 680g; 1.0L 742g
  • Colours: Black, Tangerine, Barn Red, Moss
  • Price: £35 & £40

For more info see

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7 Dec, 2016
Do you have to totally remove the conventional stopper to pour? That'll lead to a fair bit of heat loss. Normal flasks only require one to undo a couple of turns and then you can pour.
Good question: just checked, and yes you do
7 Dec, 2016
Hmmm, bit a basic design error there then.
7 Dec, 2016
That does sound like a bad design. Even the cheap ikea ones have a bypass, you you only have to turn half a turn...
7 Dec, 2016
That is surprising. My very good cheapy IKEA ones have pop up lids, but a 20 year old one I still have had a normal stopper that you could pour through after a a couple of turns. Odd they didn't do that.
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