Excellent thermos in design and functionality. Liquid stays hot for a very long time.Here's what I've tried:1. Filled it with boiling hot water. Waited for 4 hours, opened and poured to make tea. Still very hot, almost as if I'd just poured it from a kettle that has just boiled. Made a cup of piping hot tea. Closed stopper with a push of a button. Then waited for another 5 hours to make 2nd cup of tea. 2nd cup of tea steeped well, and was too hot to drink. Had to wait about 10 minutes to cool enough to take a sip.2. Filled it with boiling water. Waited for 8 hours before opening it with push button. Poured and made tea. Tea steeped well, and was still too hot to drink. Had to wait about 10 minutes so not to scald my lips.3. Filled with boiling hot water. Waited 24 hours before opening it. Although not boiling hot any more, but still too hot to drink without letting it cool for 10 minutes. Tea took longer to steep, but still was able to make decent cup of tea.Verdict:Great heat retention.Convenient to use: I like the push button pour spout; makes it very convenient to open and close without having to unscrew and screw on stopper.No leaks: For those who has complaint about it leaking, mine has worked fine since I got it a month ago. Note, however, that if you use the push button to pour, the stopper will retain a little liquid on the outside. So this could be confused for it leaking (which I had originally thought it was). Figured it out quickly, and remedied by turning thermos upside-down after push-button closing the stopper and shake off residual outside liquid. Been using thermos for over a month on almost a daily basis with no issues.Excellent design: A little on the tall side, but not an issue. And slim enough to fit nicely in a backpack. 2nd cup is a nice and welcomed touch, but haven't had the need to share with anyone yet. 1 liter size is good enough for one medium Starbuck-size, plus one small Starbuck-size cup of tea. So if you're going to share, the two of you might have to settle for 2 smaller cup of Joe. So don't expect to have lots of refills on hand. But great for one person. I use the 2nd cup as a convenient place to keep my tea bags.Well made: Even though it says "Made in China for Isosteel, Deutschland (Germany) GmbH" on the bottom of thermos (not the bottom of 2nd cup), this thermos is solid and very well made. I guess there are some Chinese clones out there as I've seen some on eBay for about half the price (but they don't say nor claim that it's an Isosteel thermos on their item description). So, I think those are the ones that leaks and are not-so-well-made. That's why I'd decided not to buy one of those on eBay, and bought this one from Amazon instead. I felt that there is a higher probability that you're getting an authentic item from Amazon as opposed to possibly a clone on eBay, as you never know what you're getting when you buy from some random seller on eBay. You could possibly get a refund through PayPal, but that's always a hassle. With Amazon, however, you have a no hassle, money back return policy that you can pretty much rely on.All-in-all, a great, this is a well designed, well made thermos. I'm very happy with this purchase, and would recommend it to others.

Hands down the best thermos I have owned. My coffee is still as hot & fresh as if I had just brewed it, even at 12 hours. That is the longest I have gone with the coffee before finishing it off, but I still have to wait for it to cool down to take a sip. I like the option of having two cups on it, plus using the bottom one as a little storage area for snacks or what not. I actually had one from this company before and decided to buy a replacement after my first one got stolen. I suspect some rat bastard that works with me stole it after making comments on how nice it was and how they wanted one. Odd that they stopped saying that after mine went missing. Don't worry I got revenge on them. Unlike my coffee from this thermos I served my revenge cold. Although with how long it keeps things hot I have to think that the cold aspect would be even greater than the hot. Hot or cold, desire or revenge, this thermos is great. You should get one. It's also sharp looking and makes people want to start up a conversation about what you have. I have had guesses of it being a bomb, something to hold nuclear material, an instrument and few other bizarre things. So if you like random conversations about how you keep your coffee hot that is just another bonus of this epic thermos.

PROS: I tested this out vs several others: 24oz ThermoFlask brand, 40oz ThermoFlask, Stanley brand 1.5 qt. thermos, & this one. Of course, outside temps will vary temperature in each thermos, but here were my results after pouring boiling in water & waiting 16 hours (in degrees): 24oz= 98; 40oz= 112; this 1 liter Isosteel=151; Stanley= 162. So this one is really excellent for insulation. Plus the double cup design is handy, and the top pour spout is a great design for easy pouring; & the price is MUCH less than the StanleyCONS: This thermos is BIG: Holding 33.8oz (1 liter), that's 14.2oz LESS than the SAME size but more expensive Stanley, & 6.2oz LESS than the shorter, thinner ThermoFlask. It's WAY too big for a day pack, fine for in a roomy car...sort of (still takes a lot of room). The top opening is a slight con for cleaning, as it's a tad small. The 40oz & 24oz ThermoFlask's are much shorter & lighter, good for a day pack, and hold heat/cold sufficiently for most day hikes, EXCEPT in cold outside temps, liquids will not stay as warm as you like, & in summer, not as cold as one might want. Overall, this durable Isosteel is a good buy for a roomy vehicle.

Very nice to have the storage space right on the thermos- can store coffee pods or other snacks. Insulation is outstanding!I use it on frigid Minnesota days at my horse barn to keep my hot chocolate and cider warm. After a few hours the liquid is still boiling hot! Fantastic item!

Bought this thermos based on other reviews and have not been disappointed. The removable bottom works for storage or a second cup, although the advertised 1 liter seems like a lot less than I thought it would be. I measured it and it is a full liter. I do have two complaints however. First, the top cup can swell or shrink and make it very hard to remove the cup. This can be a pain since the cup is smooth and makes getting a good grip near impossible. My other problem is the water does not stay hot for as long as I would like. Half a day, yes it is still piping hot, but based on the reviews, I was expecting piping hot at the end of the day, or near it. If I fill it will hot water for a few minutes, empty, then fill it with hot coffee it does stay hotter longer. Still leaps and bounds over any other thermos I've owned. All in all, a very good thermos.