Trusted by 30k+ Runners
450ml / 15oz
No-slosh Design
A Better Way To Carry Water
Trusted by 30k+ Runners
450ml / 15oz
No-slosh Design
A Better Way To Carry Water
Soft, collapsible flask custom-built to fit securely in the Endorphin Belt for distraction-free hydration on the run.
Soft, flexible design
compresses as you drink to minimize movement and noise.
High-flow, self-sealing bite valve
delivers fast hydration without drips or leaks.
Twist-to-lock cap
adds an extra layer of security during hard efforts.
BPA-free, odor-resistant materials
built for frequent use and refills.
Shaped to fit securely in the Endorphin Belt
for stable, hands-free carrying.
Stacks with the 450ml flask
for up to 700ml of total hands-free hydration on long runs.
Soft, flexible design
compresses as you drink to minimize movement and noise.
High-flow, self-sealing bite valve
delivers fast hydration without drips or leaks.
Twist-to-lock cap
adds an extra layer of security during hard efforts.
BPA-free, odor-resistant materials
built for frequent use and refills.
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30-Day Risk Free
No-Bounce Guarantee
"Great flask! Good enough for a few hours race! Super comfortable during runs."
Frequently Bought Together:
Endorphin Running Belt
Everyday training essentials
Race Bib Toggles
Keeps your bib secure
$45
Race Bib Clips
Keeps your bib secure
$45
Performance Hat
Keeps you cool on every run
Features
Custom-Built Soft Flask (450ml / 15oz) fits securely in the Endorphin Belt, keeping you hydrated without slowing you down.
Collapsible Design: This flexible flask shrinks as you drink, minimizing sloshing and freeing up space in your belt as your run progresses.
High-Flow Bite Valve: Equipped with a leak-resistant, self-sealing nozzle that provides quick sips without spillage.
Durable & Safe Materials: Made from BPA-free, odor-resistant materials that withstand frequent use and multiple refills.
Specs
450 ml capacity
Soft and flexible
Twist-to-lock top: zero accidental leakage
Self-sealing bite nozzle: effortless drinking on-the-go
Easy-to-grip cap: simple to open, fill, and wash
Free from BPA, phthalates, and PVC
Color: light gray and transparent
Weight: 33 g
Shipping & Returns
Free shipping and returns in Continental US over $60
30 day risk free trial
Features
250ml / 9oz capacity
Soft and flexible collapsible body
Twist-to-lock top: zero accidental leakage
Self-sealing high-flow bite nozzle: effortless drinking on the go
Easy-to-grip cap: simple to open, fill, and wash
Free from BPA, phthalates, and PVC
Color: black with white Endorphin logo
Fits the Endorphin Belt front pocket and rear compartment
Specs
Capacity: 250ml / 9oz
Weight: 29g
Materials: BPA-free, odor-resistant TPU
Care: hand wash, air dry with cap open
Shipping & Returns
Free shipping on orders $60+ US Orders
Free Returns US Orders
30-day risk-free returns US
Features
Modular Carry System: Both flasks are sized for the Endorphin Belt. Run them together for 700ml of total capacity, or grab the one that fits the day. Front pocket, rear pocket, your call.
Collapsible Design: Each flask shrinks as you drink, minimizing sloshing and staying quiet and stable as your run progresses.
High-Flow Bite Valve: Leak-resistant, self-sealing nozzles on both flasks deliver quick sips without spillage and without breaking stride.
Twist-to-Lock Tops: Zero accidental leakage. Lock it, load it, forget about it.
Durable & Safe Materials: Made from BPA-free, odor-resistant materials that withstand frequent use and multiple refills.
Specs
450ml + 250ml capacity (700ml combined)
Soft and flexible construction
Twist-to-lock tops: zero accidental leakage
Self-sealing bite nozzles: effortless drinking on-the-go
Easy-to-grip caps: simple to open, fill, and wash
Free from BPA, phthalates, and PVC
450ml color: light gray and transparent
250ml color: black with white logo
Combined weight: 62 g
Shipping & Returns
Free shipping on orders $60+ US Orders
Free Returns US Orders
30-day risk-free returns US
Frequently Asked Questions
How do I get the water flowing?
The flask ships sealed and locked for health and safety. When you first open it, look for the arrows and “on/off” markings on the cap. Just bit the nozzle and twist the cap slightly in the “on” direction at the same time to fully open the flow! Twisting alone may not release the full amount of water.
Does it leak while running?
A self-sealing bite valve and twist-to-lock cap help prevent leaks, even during hard efforts.
Can I use electrolyte mixes in the flask?
The flask is compatible with water and electrolyte mixes, and is made from odor-resistant materials for repeated use.
How do I clean the flask?
Rinse the cap and flask thoroughly after each use with warm, soapy water, and then let it air dry completely. The bite valve can also be cleaned a drinking straw brush. The cap may be stored in the freezer to prevent mold.
What’s your return policy?
We are confident you will love it, and offer a no-questions asked 30 day return policy. If you don't like it for any reason, let us know and we will work to make it right.
Zero leaks and I love the twist top function.
The belt and soft flask are excellent. The customer service is also excellent. I highly recommend
Only tried a couple belts and soft flask set ups before this one, and there’s no comparison. Accessibility and comfort were what I was looking for and this belt has it. Extra bonus are the locking mouth pieces so they don’t leak.
This is a great belt. I actually have two of them. I am an International Airline Pilot and I am training for the Miami Marathon. I use this belt for so much when I am on the road as it is what makes leaving the hotel room easy and knowing I have everything. I have only one issue I need replacement bit tops as I have start to have one of the flasks start to not be useable as the bite top has broken off.
Good size to fit in the belt. However the mouthpiece restricts the flow of water too much. It would be nicer if more water came out with each sip
Designed for Runners Who Demand More
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Features
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Contact Information
The Endorphin Belt Team
Endorphin Running Company, LLC
Soft Flask 450ml
Tested. Proven.
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