Hydro Flask Just Got Better – New Flex Cap Improves Insulation & Portability

Hydro Flask Wide Mouth with Flex Cap In Four Colors and Sizes Improving on something which is already a leader in its field is a tall order. Sometimes these attempts to tamper with a winning formula result in disaster. Fortunately for Hydro Flask (and their fans,) the company has managed to innovate something new which improves the Hydro Flask’s already impressive insulation and portability. Meet the Flex Cap.

The Flex Cap looks like a simple screw-on lid, but is the product of clever and careful engineering. Made from durable BPA-free TPU plastics and supported by stainless steel pivots, the Flex Cap’s most obvious feature is providing a convenient carrying strap for the Hydro Flask. A more subtle but equally functional feature of the Flex Cap comes from its ability to improve the Hydro Flask’s insulation. Using geometry inspired by nature, Hydro Flask’s new Honeycomb Insulation technology helps minimize heat transfer from the bottle.

At the moment, the only way to get the Flex Cap is to purchase a new Wide-Mouth Hydro Flask with Flex Cap. The new line of Flex Cap wide-mouth bottles are even available in several new colors, like Mango, Kiwi, Tangelo, Pacific, and more. If you were looking for an excuse to grab a new Hydro Flask, it has arrived!

(Check out our new review of the Hydro Flask Insulated Food Flask – all the perks of a full-sized Hydro Flask water bottle in a 12- or 18-ounce insulated food container.)


Getting To Know the New & Improved Hydro Flask with Flex Cap

Hydro Flask Flex Cap Honeycomb Insulation Cross-Section PhotoMy favorite feature of the Flex Cap has to be the improved insulation it offers the Hydro Flask. If you’ve read our piece on Best Insulated Bottles, or some of our other features on Hydro Flask, you’re probably already familiar with the double-wall vacuum insulation which makes Hydro Flask and other stainless steel water bottles so exceptionally insulated. This technology works by making a sort of “bottle-in-a-bottle” which is very effective at isolating the bottle’s contents from the outside world, which means whatever you put in the Hydro Flask – be it hot or cold – stays that way.

For awhile, anyway. It is pretty impressive, really, with the Hydro Flask (and similar products) being capable of surpassing their advertised ability to keep hot’s hot for 12 hours and cold’s cold for 24. Yet this design has a weak point: the lid. Easily the least insulated part of the bottle, typically just a simple plastic lid, the bottle’s vacuum insulation does not extend to its top. With the Flex Cap, Hydro Flask has tried to innovate around this problem.

Their solution is pretty clever. Not only that, we have found it to be pretty effective. Looking at the insulating properties of beehives – properties the hives achieve through the simple shape of their honeycombs – Hydro Flask’s engineers have created a design which traps air in the geometry of their artificial honeycombs, managing to further minimize the bottle’s heat transfer.

Improved Portability

Diagram explaining Hydro Flask Flex Cap Honey Comb Insulation and Carrying StrapThe other upside of the Flex Cap comes from the carrying handle. This is made from a very durable TPU plastic which is flexible and feels very nice to hold. The plastic itself is quite well-manufactured and suited to the task of hoisting your Hydro Flask day in and out, and the construction is reinforced by the inclusion of stainless steel pivots which allow you to adjust the angle of the strap.

This is a nice touch, considering the Hydro Flask has previously lacked any kind of handle or strap unless you buy separate Hydro Flask accessories. Adding an ease of portability and a comfortable way to tote the bottle, the strap is very functional and its flexibility lends it a versatility that makes it comfortable to use no matter how you prefer to carry the bottle.

Classic Hydro Flask Quality

Wide Mouth Hydro Flask with Flex Cap Sizing ChartFor all the improvements on the lid, this new generation of Hydro Flasks has more or less stuck to their classic design in terms of the bottle itself. Aside from rolling out some fancy new colors, the bottle itself has the same features which has made Hydro Flask the leading name in insulated water bottles. Made from high quality 18/8 food-grade stainless steel, equipped with the best insulation we’ve come across, finished with an anti-sweat matte coating to prevent any condensation, and made from virtually indestructible stainless steel, there is plenty to love about the Hydro Flask.

Of course, we’ve given it a lot of praise in the past. We named Hydro Flask the Best Bottle of 2015, gave it an honorable mention in 2016’s best bottles, crowned it the winner in its battle against Klean Kanteen, and named it Best Insulated Bottle. Check out any of those articles for more on the merits of Hydro Flask, or read our original review of Hydro Flask.

The Latest & Greatest


This new line of Hydro Flasks with Flex Cap is an exciting direction for the company. We are always excited to see something new from one of our long-standing favorites, and glad to see that Hydro Flask has managed to improve itself without compromising any of its great qualities. While it would be cool to see the Flex Cap available as a stand-alone accessory, the new colors provide some extra incentive to grab a new Hydro Flask to take advantage of the Flex Cap and have a stylish new color.

The Flex Cap bottles are essentially just standard wide-mouths equipped with the new lid, so accessories like the straw-lid will still fit on the new Flex Cap bottles.

Learn More about the Hydro Flask Flex Cap

To check current prices, read other customer’s reviews, learn more specific details, or purchase a Hydro Flask Wide-Mouth with Flex Cap for yourself, head on over to the Amazon listing.

Wanna see the Hydro Flask Flex Cap in action? Have a look at this brief YouTube clip from Hydro Flask to get a more animated idea of what the Flex Cap has to offer.


Brand New Honeycomb Insulation Lid
Improved Insulation
New Colors

  • Editor Rating
  • Rated 5 stars
  • 100%

Hydro Flask continues to innovate and improve with their new Flex Cap, adding additional insulation to the already renown capabilities of the classic Hydro Flask design.

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