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UltrAspire 500ml Soft Flask
UltrAspire 500ml Soft Flask
 
Price: £16.99
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Description
 
UltrAspire 500ml Soft Flask
500ml · 42mm wide opening · ~45g

A lightweight 500ml soft flask for carrying water, electrolyte drink or carbohydrate mix in compatible running vest, backpack and waist-pack pockets. Its slim, contoured shape and flexible body make it easy to carry close to the body, while the flask collapses as you drink to reduce fluid movement and sloshing.

The 42mm wide opening makes refilling straightforward at aid stations and provides enough space for adding drink powder or ice. A soft silicone bite valve provides direct drinking from the flask.

For a smaller option for lower-volume hydration or more compact pockets, the UltrAspire 300ml Soft Flask is also available.

Features
  • 500ml capacity: a common front-vest hydration size and useful as one half of a two-flask 1 litre setup.
  • 42mm wide opening: makes aid-station refilling easier and provides room for adding carbohydrate or electrolyte powder and ice.
  • Soft collapsible body: compresses as fluid is consumed, helping reduce movement and sloshing.
  • Slim, contoured shape: designed to slide into hydration pockets and sit close to the body.
  • Silicone bite valve: provides direct drinking from the flask.
  • HydraPak collaboration: developed by UltrAspire in collaboration with HydraPak.
  • PVC and BPA free.
  • 42mm accessory compatibility: compatible with the UltrAspire SoftFlask Straw with 42mm Cap, Bloddle Hose Attachment and HydraPak 42mm Filter Cap.
Specifications
Capacity: 500ml / 17 fl oz
Weight: ~45g
Opening: 42mm
Valve: Silicone bite valve
Dimensions: 9 × 4.5 × 2.5in
Construction: Flexible, collapsible soft flask
PVC free: Yes
BPA free: Yes
Compatibility

The 42mm opening accepts compatible UltrAspire 42mm hydration accessories, including the Soft Flask Straw and Bloddle Hose Attachment, as well as the HydraPak 42mm Filter Cap.

Flask fit in running vests and packs depends on the available pocket dimensions and retention system, rather than capacity alone.

Need help choosing?

Not sure which bottle or soft flask is right for your vest and hydration setup? See our Running Bottles & Soft Flasks Guide.

For help comparing the UltrAspire range, see our UltrAspire Bottle Guide.

If you are unsure about compatibility or whether this product is suitable for what you need, get in touch for straightforward advice.


Average Rating: Average Rating: 5 of 5 5 of 5 Total Reviews: 2 Write a review »

  0 of 0 people found the following review helpful:
 
5 of 5 Great fit for my UD vest Monday, March 23, 2026
Reviewer: Michal Prosecco from Basingstoke, Hampshire United Kingdom  
Over tried the branded insulated bottles before and they weren't a good for for my UD vest, as the lid was impossible to squeeze under the drawstring to keep the bottles locked in. These ones fit in amazingly well and are great value for money. Also the lid has been redesign now to bite and sip and there's no need to lock/unlock the mouth piece.

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  0 of 0 people found the following review helpful:
 
5 of 5 Brilliant Tuesday, October 24, 2023
Reviewer: Danny Phillips from Mansfield , Nottinghamshire United Kingdom  
Really like these, light weight and easy to clean and maintain

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Bottles / Soft Flasks > UltrAspire
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