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Fluid™ 18


http://www.mountainhardwear.com/fluid-18-OU4525.html OU4525


Perfect for technical outings where speed and stability are critical, this well-ventilated lightweight pack keeps day trip essentials close and comfortable.

Past Season Color
Style# 1454341
product.components.activity: Backpacking / Hiking


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      Sizing: True to Size |

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Features & Specs

  • Weight: - 1 lb. 8 oz. / 680 g.
    1 lb. 10 oz. / 740 g. -
  • Reviewers rated this product: - True to Size -
  • Pack Capacity: - 1100 cu. in. / 18 L
    1220 cu. in. / 20 L -
  • Good For: - Backpacking / Hiking -


Perfect for technical outings where speed and stability are critical, this well-ventilated lightweight pack keeps day trip essentials close and comfortable.

Past Season Color



  • Fabric Accent: 210D HexNut™ Ripstop Nylon
  • Fabric Body: 100D HT Ripstop Dobby Nylon
  • Body Fabric Content: 100% nylon
  • Fabric Bottom: 210D HexNut™ Ripstop Nylon


  • Pack Weight S/M: 1 lb. 8 oz. / 680 g.
  • Pack Weight M/L: 1 lb. 10 oz. / 740 g.
  • Pack Capacity S/M: 1100 cu. in. / 18 L
  • Pack Capacity M/L: 1220 cu. in. / 20 L
  • Pack Torso S/M: 16.0 in. - 19.0 in. / 41 cm - 48 cm
  • Pack Torso M/L: 18.5 in. - 22.0 in. / 47 cm - 56 cm
  • Pack Waist S/M: 28 in - 34 in / 71 cm - 86 cm
  • Pack Waist M/L: 33 in - 39 in / 84 cm - 99 cm


  • CoolWave Suspension with air channels and breathable spacer mesh backpanel and lumbar provides excellent load support and great ventilation
  • OTF (On-The-Fly) Compression lets user adjust load stability while wearing the pack without restricting motion
  • Large main compartment with internal security pocket
  • Front compression pocket with stretch mesh panels for overloads, helmet, etc.
  • Large zippered mesh pockets on ventilated hipbelt keeps essentials handy
  • Dedicated zip access hydration sleeve with dual ports
  • Super stretchy mesh side pockets offer quick storage/access for water bottles, hat/gloves, etc.
  • Ventilated and soft edge shoulder straps are comfortable on bare skin
  • Carry loops for ice axes and trekking poles
  • Reflective hits for high visibility and safety
  • Imported


Rated 4.7 out of 5 by 7 reviewers.
Rated 4 out of 5 by Lots of good features in a small space Great as a small day hike or trail running pack. Holds water, lunch, ten essentials, extra clothing and still has room for a summit treat. External pockets will hold 2 standard liter water bottles or use the hydration pocket. Decent sized pockets on the waist band for compass, snacks, or a phone. Two small D rings on chest straps to clip on a GPS or camera are a bonus. February 8, 2014
Rated 5 out of 5 by Everything you need Great pouches, multiple ways to use and very light. February 8, 2014
Rated 5 out of 5 by Great Day Pack I bought this for a day pack while I was backpacking. It's light and fit in my backpack without taking up too much space. We actually sent one of our packs out on a mule from the hike, and my wife used this bag packed with water and clothes. It was suprisingly comfortable and fit a bunch more than I thought it would. Great Pack! September 3, 2013
Rated 5 out of 5 by nice little bag Works perfect to put a hydration bladder in and I typically put my rain gear in it or extra layer maybe a few odds and ends. It stretches a lot from original size at first when I saw it i thought it might be to small. Used it on a recent fishing trip and hiked around in the river and at times bending over to cut threw thickly forested area's. I honestly would have forgot i had it on if didn't get thirsty. May 7, 2013
Rated 4 out of 5 by Bladder doesn't fit This bag is pretty good. The bladder pocket is only unsewn on the narrowish top. This makes it extremely difficult to insert a bladder. For example you can't have a jacket in the bag and insert a 2.5L Platypus with 2L water. You would have to completely unload the bag. Even when bag is empty, loading bladder is a struggle. Need some side velcro or strap or zipper so loading a bladder is possible. November 7, 2012
Rated 5 out of 5 by Exceptional function This is one of MH's larger hydration packs. It has chest and waist belts/buckles and a great deal of storage capacity. It feels like the perfect compromise between a true hydration pack and a standard daypack, without restricting movement. I am ~ 6'2" and 185 lbs. I am long-ledded/shorter torso, however the M/L fits just right. Call one of the MH's representatives to get guidance on sizing before selecting S/M or M/L. Great product! July 25, 2012
Rated 5 out of 5 by excellent bag! my third Fluid daypack and it's the perfect size for a full-day hiking trip. good dedicated hydration sleeve. not sure what the loop is for above the overload pocket? would like integrated rain cover for all daypacks. overall, a nice pack. April 16, 2012
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