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Aenergy ST 20-25L Backpack

4.75 out of 5 stars
4 Reviews

Out of Stock

Don't worry though, we have a lot more Winter Packs in stock than that.

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Why We Like The Mammut Aenergy ST 20-25L Backpack

On short yet demanding tours, we load the essentials in the Mammut Aenergy ST 20-25L Backpack. From our ice tools to our helmet, there's a lash point for everything, and the front zippered compartment keeps our avy gear organized and easily accessible. When the skintrack turns into a bootpack, we click out of our bindings and attach our skis to this pack without taking it off. As we climb, the running-vest-inspired harness system keeps our carry high and stable, while the stretch sternum straps let our lungs expand freely on the final push. Along the sketchy ridgeline, we remove the top compression strap and use it as a waist belt for added stability as we make our way to the drop-in point.


  • Compact, body-hugging pack for your fast and light tours
  • Vest-style harness system delivers a steady, low-profile carry
  • Roll-top closure offers versatile capacity of 20 - 25 liters
  • Back zipper gives you alternate access to main compartment
  • Front zipper compartment secures your avy equipment
  • Attachment points for skis, ice axes, poles, rope, and helmet
  • Dual daisy chains let you lash on extra gear
  • Mesh shoulder strap pockets stash snacks and radio
  • Item #MAMU5S7
100% nylon
20 - 25L (1220 - 1525cu in)
Contact system
Shoulder Straps
mesh, 2 adjustable sternum straps
Waist Belt
compression straps can double as a waist belt
Hydration Compatible
Reservoir Included
roll-top, back zipper
1 front avy, 2 mesh shoulder strap
Ski Carry
speed attachment
Helmet Carry
Ice Axe Carry
21.26 x 11 x 7.87in
Claimed Weight
1lb 8.3oz
backcountry skiing
Manufacturer Warranty
limited 2 year

Overall Rating

5 based on 4 ratings

Review Summary

1 Stars - 0 reviews
2 Stars - 0 reviews
3 Stars - 0 reviews
4 Stars - 1 reviews
5 Stars - 3 reviews

Fits True To Size

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What do you think about this product?


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4 out of 5 stars

March 16, 2024

Mammut Arnergu ST

I've used it several times
Size Bought:
20-25 L

The pack is well made and functions beautifully. The straps fit well, albeit a little cordy. A small outside pocket for things like phone, ID, or multi-tool would be a nice add.

5 out of 5 stars

February 22, 2024

Versitile and Light

I've used it several times
Size Bought:

I've had a few Mammut packs over the years. I'm a former ultra-runner, turned skate skier, and needed something to carry a few essentials, yet have space for my down jacket when things got ugly. I've been wearing it this season and absolutely love it. It stays out of your way, doesn't bounce around thanks to the vest-style shoulder straps and sternum cords. I do still trail run, and will be taking this for some longer excursions through the woods. Also, I have a larger frame and was concerned with sizing, but the Large size is a perfect fit for my 6' 200+ frame.

Mike S.
5 out of 5 stars

February 26, 2023

Perfect for ski touring

Just the right blend of features to keep things useful and lightweight.

Originally reviewed on

5 out of 5 stars

December 2, 2022

Great pack

Love the front storage pockets and the lightweight feel. I use this pack for dawn patrol and longer ski traverses when saving weight is critical.

Originally reviewed on