Slight concave on bottom of cup. As one can see by pictures, a concave bottom, as nearly all cups and mugs are, is not useful with a warmer. However, this one is very slight and heat transfer is still decent. And a nice look, thus, 4 stars.

Beautiful, just what I wanted.

I really like these mugs. They are lightweight and seem to be good quality. I would definitely buy thesr again.

I bought these for my 95 year old mother because other drinking glasses with handles were too heavy. These are perfect. She uses them for water and they are easy to hold as well as lightweight. Very happy with this purchase.

These glass mugs are EXACTLY what I needed for my Coffee Mug Warmer that works best when paired with a flat bottom mug. I was a little concerned after reading reviews that stated these break easily, but I’ve had mine for nearly a year now, and they’ve held up without an issue. I will agree that they do feel very delicate, but I compare them to a regular glass coffee pot - feels delicate, but very sturdy.

Was a bit disappointed on the quality of the mugs. I thought the mugs to be “thin,” if that makes sense. Used for gifts, found myself a little scared handling them thinking they would break. They’re useable and I’m happy with the style. What, again, throws me off is the flimsiness of the glass itself.

I have ran it through the dishwasher a couple times and used it a few times now. So far they are holding up. Capacity wise I ordered the 18oz ones and I did measure it to ensure I got the right capacity and it does fill 18oz right to the rim. What I do really like about these mugs is the bottom is perfectly flat. I got an electric mug warmer and non flat mug bottoms (basically ones that have a lower rim around the bottom) don't sit flush on the heated surface. Since these have a true flat bottom it does sit flush on the heated surface and it works better keeping my drink hot. That is important to me as I often get distracted from my drink and forget its there till like a hour later and it is still hot for me.

I bought 4 of this and am really very happy with them. They are light weight and sturdy, but not thick or heavy glass which I don't like. I would like the glass even thinner, but as they are they are just fine. A nice quality mug for a cuppa. Would definitely recommend.

It took earlier than I expected and also these cups are so cool. Thank you so much. Definitely recommended and will order again😁

I purchased these mugs because I decided to try a mug warmer and needed mugs with flat bottoms (to work better with warmers) and single walled construction. After much research, these mugs are about as flat as you can get and work great with my new warmer (Ingecafea Upgrade Coffee Mug Warmer for Desk Use - https://www.amazon.com/gp/product/B09BQM8DJK/ref=ppx_yo_dt_b_asin_title_o03_s00?ie=UTF8&psc=1)Beware that these mugs are very light, being made of borosilicate glass. I knew this going in as I have other mugs made of the same stuff. You have to handle them a bit more gently than regular, heavy ceramic mugs. So far they have held up well for my usage (including in the dishwasher), but I'm careful not to bang them around or hit other objects when putting them back in the cabinet.I purchased the 17 oz version. FYI, it holds exactly 17 oz when filled to the very top. I saw some complaints in reviews because folks wanted it hold 17 oz plus room for cream. Also know that the handle is large enough for 4 fingers, but it's a bit cramped. I'm a male and it fits 3 fingers very comfortably. I would have preferred a 4 finger fit, but I realize the size of the mug probably dictated the handle size.Now with the new mug warmer, I can sip on my coffee for several hours while at my desk and it stays nice and hot! The above mentioned mug warmer works great too!

Although these cups are made of thin glass and cost more than I wanted to spend on a mug to use with my new electric cup/coffee/tea warmer, these are the only cups I could find that will work with my cup warmer. Not one coffee mug available on Amazon, or anywhere else online, that has a flat bottom. Every mug has a narrow rim and the rest of the bottom. Is concave, and so won't touch the heating element which keeps cup and coffee hot for hours. Who uses a delicate glass mug for daily and repeat use? Glass breaks very easily, and thin glass especially, and they also chip very easily. I have a cabinet full of coffee cups, most have a picture of my dog or cat on them, but they all have that same bottom which doesn't work with any cup warmer. Most of us have a mug from some event or other, gratis, I just paid $8 for a very plain glass mug because it's the only cup on the market that has a FLAT bottom. Now normally I would not have spent that kind of money for something I already own more then I need. And glass, thin glass, glass coffee cups I would maybe purchase for entertaining.. I have to admit that a cup of dark coffee or hot chocolate, both with a good dollop of whipped cream on top, that does look impressive in a glass cup. That's elegant and that's why I would buy glass cups, to show off to my guests. The thing is, I don't entertain like that anymore, too old ;-)I am mostly bedridden but still do everything for myself. I wanted a coffee warmer, or tea, I drink a lot of tea every day. I have been using these glass cups on my new cup warmer and I am very glad I purchased these glass cups. They are perfect! The cup fits perfectly on the heating element of the warmer and keeps my tea hot all day - hot, not just warm!I heat the water in the glass cups in the microwave, fix the tea and then bring it into my bedroom and on the cup warmer. I just suffered through two weeks of a stomach bug and practically lived off tea and chicken broth. I even purchased a second cup warmer. They are small and both fit on my night table. So I keep a cup of tea and a cup of chicken broth hot until I'm done with either. I wash the glasses by hand and in the dishwasher, I heat the tea or broth in the glasses in the microwave on high for 1 1/2 minutes, and I do this several times a day, done it every day for the past two weeks. I can tell you that I am glad I purchased these glass cups.These glass cups are just great. Yes, I handle them with care to prevent a typical glass thing, glass breaks much easier then a good ole mug. So, no, I'm not complaining about the cost nor the glass, they are actually beautiful sitting there with clearly visible the beautifully deep red Rosehip tea and the rich chicken broth. No guessing which is which.I can't tell you just how much it helped me these last two weeks, having tea and broth ready to sip hot.Eventually the market will catch up with the need for mugs, regular mugs with pictures of our pets and our kids on them and with a truelly flat bottom to accommodate all people who work in an office and just anyone who owns a cup warmer.Until then I will drink my tea from my fine and elegant glass cups. And on second thought, I deserve a little luxury, LOL.,

These are advertised as 400ml measuring cups. The assumption is that you can measure in ml.The cups are very smart but they only have measurements marked in fl ozs on one side, with the other side being totally blank!I have never purchased any measuring jug or cup or glass that did not allow you to measure in imperial and metric.If you are purchasing these for cooking purposes, beware!

Love the look of these mugs ...I always have glass mugs and these are the sturdiest and the largest I've had..will be buying another set as the only downside is that I wanted 6 and they only came in a pack of 4