Product Colors and Sizes

  • Sale product
  • Best Seller product
  • Eco-Friendly product
  • New product
  • Staff Pick product
  • In The News product
  • Innovation product
  • product

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult

Sale price: $12.99 Regular price:

Make yourself comfortable during your trail runs. Thanks to its flexible shape, your 500 ml flask is easy to carry in hand and can be easily stowed away in your bag or trail running jacket.

Color: Select a color
Size: Select a size
Sale price: $12.99 Regular price:

Free returns

Free shipping over $35

Free pickup

San Francisco, 735 Market St. Options

Select an available color and size to see options.

Model: 8600920

Product Features

A photo of the Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult in use

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult is designed for

Make yourself comfortable during your trail runs. Thanks to its flexible shape, your 500 ml flask is easy to carry in hand and can be easily stowed away in your bag or trail running jacket.

Compact design

Save space thanks to the flexible and compressible material of your flask.


Your flask will remain silent while you run by easily removing the air inside.


Run and feel light: your flask weighs only 1.2 oz when empty.

Easy to use

Drink easily thanks to the opening system that involves rotating the mouthpiece.

Mouth comfort

Run comfortably with the accessible silicone bite valve for mouth comfort.

Product Lifestyle Image Gallery

Image Gallery

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult,base color 

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult,base color 

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult,base color 

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult,base color 

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult,base color

Product Customer Reviews

Skip to reviews
512 Reviews
Write a Review 

Kalenji 2020, Flexible Trail Running Flask 500 ml, Adult,base color
Filtered by reviews Loading reviews…
Kalenji Soft Run Flask 500ml

Great narrow shape and fits well into my Salomon run vest, love the Open/Close twist valves too!

icon-circle-checkmark verified purchase
good quality and very useful

Can i wash it by dishwasher?

Great bottle

Perfect size for pocket or for holding.

icon-circle-checkmark verified purchase
useful item

This is a very useful item for my runs

icon-circle-checkmark verified purchase

Light and easy to use, these are exactly what I expected and hoped they would be. They were a good fit in the hydration vest.

The plastic taste does go eventually

Drinking straight from bottle, proved the main cause of the plastic taste was the teat. Separating and soaking the bottle and teat underwater for a couple of hours removed most of the bad taste. After many uses and soakings the bad taste has gone. Much better that all the other bottles and hydration packs that I have.

icon-circle-checkmark verified purchase

I got two of these to use on my trail running packs, just right.

icon-circle-checkmark verified purchase

As expected a good product

icon-circle-checkmark verified purchase
Premium product at a reasonable price

These are great soft flasks. The bite valve works very well and the added twist on/off means no leaks. There is a removable tab can be used to clip it on to bags etc. Given the price compared to some high end flasks, this is a fabulous product.

Great product

Swapped from bladder to flasks really please with my purchase

icon-circle-checkmark verified purchase

Work really well in the vest once I worked out how to use the drinking cap. Needs a good clean to remove the rubbery taste before use.

icon-circle-checkmark verified purchase

Great water pouch, my only downside, is I wish the filling hole was bigger, but great apart from that

icon-circle-checkmark verified purchase

I was trying to use this bottle several times, I washed it a few times with water but it is still smelly. I took it for a few short runs and I wasn't able to drink the water, because of plastic taste. I had that kind of bottle in the past and it was fantastic I used it for a year or more but it was different material and prudent. I am really disappointed.

Soft Running Flasks

These flasks are superb, we now have six, my wife uses them with her Kalenji (I call them running vests), they are in fact Hydration Back Packs, she has two, used for trail running here in sunny Cornwall. Decathlon should make spare tops available, perhaps selling them in pairs, I have two flasks with a top problem, one has a slight leak, another has a damaged top after one of my dogs decided it would make a great toy, so well chewed. I usually mix her drinks the night before, I place them in the refrigerator over night this chills the liquid down making them much easier the place in the vest pockets.

icon-circle-checkmark verified purchase
Great product

Think these used to be £5... but they're probably worth the £10 they are now though that's not much cheaper than the Salomon ones. I've had them for over a year, so used 50+ times for lots of big runs and cycles with them in Decathlon's (also great) ultra vest and they don't leak, are easy to fill and can drink from them hands free. Can fill one with gels for longer ultra runs and I have never noticed a bad taste from mine. I haven't had any issues at all with moulds though this might just be luck.

Skip to reviews

Additional Product Information



  • 100% Thermoplastic polyurethane

On/Off System

  • 34% Polypropylene
  • 66% Polyethylene low density


  • 100% Silicone

A flexible flask making your trail runs more comfortable.

Offering you flexible containers for your trail runs is the aim of our design team. Compared with a rigid water bottle, your flask is lighter, less noisy when you run and does not hinder your movements as much. What's more, it occupies less space: You can compress it gradually as you drink the contents, thereby reducing its volume!

How to maintain your flask?

To prevent any taste of plastic, rinse your flask in clean water 3 times before using it. Then, dry it upside down without the mouthpiece. If the plastic taste persists, place your dry flask in the freezer. You can remove the mouthpiece to clean it. This is particularly important if you are using sugary drinks! Finally, so that it doesn't make noise while you are running, remember to remove any air by sucking out the air bubbles.

What is the flask's running time and what is it compatible with?

With its 500 ml capacity, your flexible flask is useful for about 1 hour of running time, on average. And in order to simplify your preparation and equipment, your 500 ml flask is compatible with all our trail running bags and belts!

A user-friendly design when trail running.

Your 500 ml flask has a thumb hole. It can therefore be carried effortlessly even when you have pushed yourself to the limit during your trail run. The mouthpiece of the flask has an on/off position. In the off position, you can avoid any nasty surprises during transportation. In the on position, your flask will not leak while you are running: Pinch the mouthpiece and suck to drink. Finally, the flask is designed so that you can drink without removing it from the front pocket of your bag.

How was the 500 ml flask tested?

To guarantee the quality of the 500 ml water bladder, our design team asked 12 runners to use it during a running session on a treadmill. Much more relaxed than a trail run, running on a treadmill gives you the opportunity to concentrate on the flow rate of the mouthpiece, the taste-free water, the lack of any discomfort when using the mouthpiece, the movements of the flask, and the user comfort. With the help of the feedback provided by our testers, we designed a product for trail running.



Product testing

At DECATHLON, our products are tested by a panel of users under the real-life conditions they were designed for. These tests are coordinated and supervised by a team of engineers dedicated to this mission. The product managers, engineers, and all the teams use the results of all these tests to develop and design technical products that will satisfy our trail runners.

Storage instructions

Rinse the flask thoroughly 3 times when using for the first time. Do not leave water in the flask for more than 24 hrs. Rinse it with clean water after use and allow to dry before storing.

Superior quality. Unbeatable prices.

For 40 years, Decathlon has delivered the best value in the retail sports industry by offering high-quality, sustainable and cost-effective products.

Decathlon makes the difference
  1. product-research

    Research and development

    delivers high-quality cost-effective products

  2. State-of-the-art production processes

    minimize manufacturing costs

  3. Optimized supply chain

    reduces retail prices

  4. laptop-checkout

    Minimal retail footprint

    lowers overhead and indirect costs


Size Guide Visual