Good addition to your flask
597646
When I bought my 64oz hydro flask I knew I wanted something that wouldn't require me to unscrew the lid and then have to screw it back on, found this sip lid and has been good, pop the lid and get a drink, then pop it back down. Sometimes though the ice inside will block the hole. Good addition to your flask
186594
These are great little flasks and I like that they come in a couple of different sizes to it my needs.  Washable, flexible and most of all, easily concealed, as this is the intended purpose of these flasks.  They are also good to carry fresh water in your cooler so you aren't having to pay for bottled water, and they have a flexible/flat sort of fit so they aren't taking up a ton of room in the cooler like bottles do.  Comes with a nifty little funnel to make filling easy.  I am attending a three day concert soon, and this will keep me from having to pay premium prices for a bottle of water that I won't even be allowed to keep a lid for.  Well, and maybe one of them will contain a little something more fun than water. :P  Easily worth the money I will save at the concert.
2974156
It is a simple, solid addition to a Nalgene bottle.  I carry my Nalgene  with me wherever I go,  so no I won't leave home without my supplements too! I also like that this makes the lid  just heavy enough that when you open the bottle and drink, the lid hangs out of your way.
3633014
I used it every day at the beach while working in hot weather and the flask was still able to keep the water cold. I refilled it once a day, but I'd rather do this than have to carry around ablarger, heavier bottle. The flask doesn't give the water a weird flavor like many plastic bottles do.
932690
I love my Hydroflask. I love it even more now that I have this cute silicone cover. It makes the HF much easier to handle. Plus, I dropped my flask a while back and it had a small rough patch. Now, I don't have to worry about it.
3527323
My brother and I successfully snuck two flasks of single malt scotch whiskey into an NFL stadium. Now, we weren't patted down, but the flasks weren't detected when we were wanded. They hold a decent amount of fluid, and we're fairly easily conceled. We chose to put them under the front part of our pants, with our waistband holding the spout. They did not leak, however the flasks were kept upright, and not completely filled. I like the fact that they are flexible, and not hard plastic. It was also nice to have the funnel to help fill the flasks. Drying them out might be problematic. We'll see how they hold up next use, but for $8, these guys already saved us money.
2181976
Flask is perfectly fine.  My only complaint is your fingerprints are continually all over it, but just shine it up....at least it is not very dull.  Cute, very lightweight and works.  Great seller/sender.  In fact, we are purchasing one more for someone else..  This is not something heavy duty, however.
2589672
Does exactly what it's supposed to. Holds about 8 shots of whatever liquid you want. It would have been nice to receive a funnel, but I came up with my own quick contraption to transfer liquids into it. Cleaning is not so easy, but if you leave it in hot water with some dish soap, it cleans itself.
1549097
This flask does not leak, is small, fits in my front pocket easily.  I used it on a cruise recently and it was handy to bring with on and off the boat.  Saved quite a bit of money buying expensive drinks when the sodas are free!  I dropped this a few times and it has held up well.  You may want to get a filling funnel as the opening is very small (although if you have steady hands it is fairly easy to fill as-is).
3085842
This is an average type flask. What is nice is the fact it comes in a gift box. I really like that it comes with a funnel, as well. That is very helpful to have. It feels like it is aluminum because it just feels sort of light and easy to damage. I had no problem getting the top open but it was little tricky getting the top back on. I just had to maneuver it around a little until it lined up just right. Then it went on without any problems. This is good for a first time flask for someone and the fact it comes with a funnel is pretty cool. I received a discount on this for testing purposes.
1683904
Nice, doesn't pour too fast or too slow, and didn't make a mess.  They look nice and appear to be quality.  The top pops off, and then the bottom silver portion is a sleeve that slides down over the glass bottle.  The silver bottom section can be removed, revealing the glass, and makes that easy to put in the dishwasher.
1519005
Works fine on my Hydro Flask Bottle and I like the change in color from the Black and Gray that Hydro Flask sells.
3334542
This is a cool flask, the funnel sits securely on it so that you can fill it up. HOWEVER I can't get a good grip on the part that I assume you hold to unscrew the shot glass. Does anyone have a tip for me on how to get this confounded thing off so I can use it???
2545036
I bought this for my wife and I ended up stealing it from her.  I feel it does a better job than my wide-mouth Hydro Flask on keeping the heat, while the funny loop on top is useful for carrying when I have many things in my hands.
3508860
The tapered contour feels nice when holding it and feels sturdy enough to take a drop on concrete. I think for the money this is the flask to have.
1481310
Perfect addition for my hydro flask. Makes it much easier to carry, very durable. And like the fact it adds color choices.
1306312
the straw is a must have attachment and it makes drinking from the large mouth hydro flasks actually feasible!  really nothing to it just a straw that works with the hydro flask.  it comes with 2 straws and you can cut them to length depending on your bottle.