Ultimate Performance Aire Flex 18L review: great-value multi-sports pack with a few issues for runners

The Ultimate Performance Aire Flex 18L is a durable running pack with two 500ml soft bottles, helmet hammock storage and reflective details

Ultimate Performance Aire Flex 18L
(Image: © Claire Maxted)

Advnture Verdict

A robust, great value, large-capacity multi-sport pack with a lot of great features for mountain bikers and runners, but room for small improvements in the front pocket area to make things more accessible.


  • +

    Robust, durable fabric

  • +

    Comfy carry of large load

  • +

    Soft bottles included (2 x 500ml)

  • +

    Can fit a 3L hydration bladder (not included)

  • +

    Reflective details

  • +

    Helmet hammock storage

  • +

    Can fit larger frames thanks to adjustment straps at waist

  • +

    Multi-sport use


  • -

    On the heavy side

  • -

    Front pockets not as accessible as they could be

  • -

    Lack of waist area pockets because of the adjustment straps

  • -

    No pole attachments

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Ultimate Performance Aire Flex: first impressions 

The Ultimate Performance Aire Flex 18L is an interesting multi-sport pack rather than a hydration pack specifically for running. If you’re only into running, look elsewhere now because you can find much lighter packs than this 570g / 20.1oz specimen, with more easily accessible pockets up front.


• List price: £80 (UK) / $100 (USA)
• Weight including bottles: 570g / 20.1oz
• Bottles: 2 x 500ml soft bottles
• Colors: Black & Blue
• Capacity: 18L
• Fit: Unisex
• Sizes: One size, adjustable
• Compatibility: Medium to long days out on the trails, suitable for running and biking

However, if you want a pack that will also work for mountain biking this could be for you. One upside to the heavier weight is that the pack does feel bombproof with good quality zips and thick, densely woven fabric – you’re not going to rip this if you snag it on a bramble. 

This pack will also suit you if you’re a larger person who struggles to find a good fit in the waistcoat-style running packs as the side straps provide a great range of adjustment up to XXXL; sadly this does mean this pack misses out on the opportunity for a couple of pockets around the waist, but you can’t have both features. 

It’s great that a pack that has such a low price tag comes with two 500ml FlexiFlasks plus straws. However, the bottles somewhat obscure the two pockets behind them, and the stretch pocket on front of the bottles is a little on the small size.

Ultimate Performance Aire Flex: on the trails

Ultimate Performance Aire Flex 18L

The Ultimate Performance Aire Flex 18L is a little on the heavy side for runners but worth considering if you’re a mountain biker (Image credit: Claire Maxted)

There are certain things this pack does really well, but we think there’s an opportunity to make the next version even better for runners with a few small tweaks. 

Although a little on the heavy side for runners, it’s a great price for a multi-sport pack with a great capacity, durability and a way to carry a helmet. The adjustability at the waist is also a plus point if you prefer that to having a couple of pockets there (good for larger sportspeople and / or mountain bikers). There’s plenty of room for a great deal of kit, and a hydration bladder compartment too if needed, while the reflective details are great for being seen on dark nights.

Ultimate Performance Aire Flex 18L

The adjustability at the waist of the Ultimate Performance Aire Flex 18L is a plus point if you prefer that to having a couple of pockets there (Image credit: Claire Maxted)

The front zip pockets are good for long items like your smartphone, gels or cereal bars and it’s really easy to drink on the move with the bottle straws. However, the elasticated pocket right behind each bottle is pretty much impossible to access, especially when the bottles are full of water, so we think these should be moved in front to replace the stretch pockets at the base, which are a little on the small size currently. If these were twice the size and they would happily take a pair of light running gloves and some snacks, which runners in particular appreciate being easy to access up front.

Claire Maxted

The co-founder and former editor of Trail Running magazine, Claire now runs the YouTube channel Wild Ginger Running, creating films about trail- and ultra-running advice, inspiration, races and gear reviews. An award-winning journalist, writing for outdoor and adventure sports magazines and websites, Claire's first book, The Ultimate Trail Running Handbook (5k to 50k), is out now. Her second, The Ultimate Ultra Running Handbook (50k to 100 miles), is out Autumn 2024. Claire also speaks and presents at events and races.