Stanley Master Series Flask Review

© UKC Gear

It's not remotely a lightweight option, and nor is it even slightly a budget buy, but Rob Greenwood is blown away by the sheer effectiveness of this insulated flask.

When I was first asked to review this a few months ago my heart sank: how do you talk about a thermal flask? Looking back to Dan Bailey’s recent review of the Primus Trailbreak EX Flask I felt his pain, as the biggest point of difference seemed to be its colour rather than its performance. This led me to wonder what other benefits you could possibly wish for from a flask, and to my mind there are only two: the first being to keep things warmer for longer; and the second being to make it lighter. The Stanley Master Series Flask succeeds in the former in a way that I have never seen before (and I’m not just saying that). However, because it scores amazingly well in terms of insulation, it rather falls down in terms of weight saving. Life is a compromise, after all.

So here’s more on how it performed…

Stanley Master Series 1.3L Flask Review  © UKC Gear
Stanley Master Series 1.3L Flask Review
© UKC Gear

As suggested above, the Stanley Master Series Flask is unlike any other that I’ve previously used, insofar as it genuinely keeps things warmer not just for a bit longer, but a lot longer - up to 40hrs for the 1.3L version. In fact, it's so noticable that I've actually had to change my brewing habits, and I now frequently make the flask night before, simply so I’m prepped and ready for the next day (always a bonus), and because it’s guaranteed to be warm when I drink it 24hrs later. Not just warm either, but genuinely hot! Maybe even too hot... Furthermore, once you start to drink it - thus let cold air in - rather than cool the rest of your precious beverage down it maintains temperature quite remarkably. If there were to be one disadvantage of its insulating properties, it is that it maintains temperature so well that often it leaves things too hot to drink straight away. Still, better too hot and leave it to cool than too cold.

If you want to understand a little more about how they achieve this it's worth checking out the following video:

Each of the components exudes craftsmanship, with an insulated mug that'll keep your already piping brew warm for around 20mins, and also features a nice matt finish with smooth stainless finish around the lip. The stopper is secure, leakproof, and doesn’t feature any moving parts nor anything awkward to clean. It also has a steel lined pour, so your brew doesn't come out with that strange plastic taste that seems to contaminate every cup of tea/coffee you've ever made in cheaper flasks (you know it's bad when each brew just tastes generically 'flasky'). Essentially, the flask and all its components are built to last. Having used - not to mention dropped - it a lot over the past few months there doesn’t appear to have been a single scratch, which is more than can be said for a lot of my other flasks!

Stanley Master Series - Cup
© UKC Gear

Stanley Master Series - 1.3l Flask
© UKC Gear

Stanley Master Series - Screw Top
© UKC Gear


Going back to my original statement: there are two major ways in which I see flask development taking place - either greater insulation (which this does) and or lighter weight. The Master Series most certainly does not achieve the latter. At a whopping 1.25kg (my meqasure) the 1.3 litre model is something of a beast. Whilst I don’t mind taking this out on short walks, days bouldering, sport climbing, or trad climbing, it’d definitely not be in my pack for long mountain days or Scottish Winter, which is a shame because that’s where its benefits would be most greatly felt. That said, it’s worth highlighting that I am reviewing the 1.3L version here and the 750ml version may well be more appropriate for those bigger days (although I do like drinking a lot of tea whilst I’m out…), as it comes in at a lighter weight. In addition to this it doesn’t feature the handle, which I felt was a bit of an unnecessary luxury for any self respecting climber, hillwalker, or mountaineer.

If there were to be one final caveat it would be price, as the RRP of £75 is undoubtedly a hefty one when compared to its competitors. Still, seeing as there is functionally a difference I see this as justified. Having bought many flasks over the years the one thing I've learned is "buy cheap, buy twice" and with that in mind this is definitely a flask for life.


The Stanley 1.3L Master Series Flask is undoubtedly something of a revolution in terms of its insulating properties and exudes quality from every angle. As such it'll no doubt be of interest for anyone wishing to invest in something high quality - albeit at a price (although a price I would say is worth it); however, and this is a big however, anyone looking at making that purchase needs to ask themselves about how much the weight matters to them. If it's an issue it could be worth downsizing to the 750ml version or the smaller Master Mug.

Stanley say:

The Master Vacuum Bottle is made for the toughest of the tough. For those who demand the very best in durability and performance, the QuadVac™ insulation keeps hot drinks hot for longer. No matter what you are doing or where you are going, this bottle is ready when you are.

  • 1.0mm 18/8 stainless steel – the strongest you’ll find by far. Rust-proof + naturally BPA-free
  • Steel-lined pour through stopper – no plastic contact for contents
  • Vacuum insulated 18/8 stainless steel cup keeps drinks hot 20 minutes
  • Dishwasher Safe
  • Lifetime Warranty

For more info see

Vacuum Bottle 1.3l
Price: £74.99
Weight: 1.3kg
Hours: 40 hours hot, 35 cold, 160 iced

Vacuum Bottle 750ml
Price: £59.99
Weight: 900g
Hours: 27 hours hot, 27 cold, 100 iced

Master mug 532ml
Price: £39.99
Weight: 508g
Hours: 12 hours hot, 16 cold, 48 iced

Support UKH

As climbers we strive to make UKHillwalking the kind of website we would love to visit, with the most up-to-date news, diverse and interesting articles, comprehensive gear reviews, breathtaking photographs and a vast and useful logbook system. As a result, an incredible community has formed around the site - we’ve provided the framework but it’s you who make the website what it is today. If you appreciate the content we offer then you can help us by becoming an official UKH Supporter. This can be a one-off single annual payment or a more substantial payment paid monthly or yearly which includes full access to Rockfax Digital and discounts on Rockfax print publications.

If you appreciate UKHillwalking then please help us by becoming a UKH Supporter.

UKH Supporter

  • Support the website we all know and love
  • Access to a year's subscription to Rockfax Digital.
  • Plus 30% off Rockfax guidebooks
  • Plus Show your support UKH porter badge on your profile and forum posts
UKC/UKH/Rockfax logo

16 May, 2017
All I have to say is thermos ultimate. Make hot choc at 0615 before a day of Scottish winter climbing on the ben. Open it at 1945 and burn tongue on drink.
16 May, 2017
It was pointed out recently that many of my comments regarding gear reviews expressed disbelief at the price of the gear being reviewed. I thought I'd be able to hold off commenting for a while but this one is the biggest joke yet. £75? Seventy five pounds? For a thermos flask. OH. MY. GOD. I can't believe what I've just read. Edit: In March, my girlfriend and I drove down from Sheffield and had eight days in Devon which cost us slightly more each than the price of two thermos flasks. Unbelievable.
16 May, 2017
To an extent you do get what you pay for. I have a Thermos 'thin and light' ( or something like that), which is massively better insulated than the average, even with big dents in it. However, the flask being reviewed is ridiculously expensive for what it is. (Although I do like the fact it doesn't have one of those f***ing stupid lids with the pouring mechanism).
16 May, 2017
Definitely the mutt's nuts. We have three of various sizes. Cost around £20-30 depending on size.
16 May, 2017
:) Simes - a review thread just wouldn't be a review thread without one of your comments! :) Actually, I'm rather inclined towards your perspective on this. I remember reviewing a base layer that was jolly good, but I couldn't really say that it was 10 times better than one from Decathlon because that is how much it was - about 10x the price of cheap alternative. I'm sure this is a great flask but it's about 20 x the price of my big one I got in Asda, and my Asda one works very well, so can it be 20 times better? But I guess price and quality aren't in a neat relationship like that.
More Comments

Loading Notifications...
Facebook Twitter Copy Email