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Item # MHW004C

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Item # MHW004C

A lightweight hybrid pack for ultra-runners.

Ditch the bouncing waist pack for the Mountain Hardwear Fluid Race VestPack, which carries the gear, fuel, and fluids you need for a long haul on the trail or pavement. The wide vest-style shoulder straps comfortably haul a hydration bladder, windbreaker, and snacks, and the mesh panels keep you cool and comfortable from mile one to 101.

  • HexWall mesh with Power Mesh panels
  • Stretchy, low-profile main compartment
  • Easy-access hydration sleeve with multiple ports
  • Quick-access shoulder strap pockets
  • Zippered internal security pocket
  • Wide shoulder straps with two chest straps
  • Reflective accents

Tech Specs

[body] HexWall mesh, [accent] Power Mesh, 100D HT ripstop dobby nylon
370 cu in
[external] 2 shoulder strap, [internal] 1 zippered security
Claimed Weight:
8 oz
Recommended Use:
ultra-running, running
Manufacturer Warranty:

Size chart

Mountain Hardwear

Women's Tadita 50, Women's Lomasi 60
Pack Size S M
Torso Range 14 - 16.5in
(36 - 42cm)
16 - 19in
(41 - 48cm)
Waist Range 26 - 30in
(66 - 76cm)
29 - 34in
(74 - 86cm)
Via Rapida 35, Direttissima 46, Molimo 70, South Col 70, BMG 105
Pack Size S M L
Torso Range 15 - 18in
(38 - 46cm)
17 - 20in
(43 - 51cm)
19.5 - 22.5in
(50 - 57cm)
Waist Range 27 - 31in
(69 - 79cm)
30 - 35in
(76 - 89cm)
Wayback 30, Fluid 32, Fluid 26, Fluid 18, Splitter 38, Fluid 48, Wandrin 48, Wandrin 28
Pack Size S/M (REG) M/L (LARGE)
Torso Range 16 - 19in
(41 - 48cm)
18.5 - 22in
(47 - 56cm)
Waist Range 28 - 34in
(71 - 86cm)
33 - 39in
(84 - 99cm)
Kanza 55, SummitRocket 40, Thruway 50
Torso Range 17 - 20in
(43 - 51cm)
19.5 - 22.5in
(50 - 57cm)
Waist Range 30 - 35in
(76 - 89cm)
How to Measure Back Length:
Measure from your C7 vertebrae (the one that sticks out from your neck) down your back in a straight line to the same level as the top of your hip bones.

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Unanswered Question

How wide are the two bottle openings? Will they fit a Nathan SpeedDraw flask?

Nice minimal pack with a major flaw

    I needed a lightweight pack for ultrarunning and this seemed to fit the bill nicely. I am 5'7" / 130lb and the S/M fits perfectly (not too small like some have said). The reservoir pocket is decent size and seems very water resistant so good for carrying gear as well. There are several zippered pockets, very small but functional on the front and one in the reservoir that just fits my iphone 6. Now for the major downer: The bottle pockets are plenty wide and deep inside, but the top opening is so small that I can barely fit a 10oz bottle much less a 17-20oz that I would like to carry on the front. It is a very unfortunate design, but I will have to send it back because this is a deal breaker for me. If you only need the front pockets for gels, etc this is a nice vest. But if you want to carry bottles forget it. Note: The race vest (slightly lighter) has wider pockets that do fit a 17+ oz bottle, I think this is because there is no zipper beside the opening like the vest pack.

    Bouncy Bouncy

    • Familiarity: I've used it once or twice and have initial impressions

    I purchased this pack to use with a 2L bladder and the occasional windy day jacket. After a short little test run I shall be returning this thing.

    The set and forget straps were in the same place at the end of my run as they were in the beginning. How many packs can claim that?
    Compression: There is none. I have forgotten how much a hydration bladder can bounce, this is worse than anything I ever tried in a decade. There is also no gear compression in the main compartment so anything more rigid than a jacket will rattle like an angry bell. To continue with bladder issues, the drink tube clip is at a useless spot on the left shoulder and there are no dedicated tube holes for an over-the-shoulder tube routing.
    I'm 5'8" 155lb and got the s/m size. with a tshirt and a fully loaded vest I've cranked the chest straps nearly to their tightest, this is not a pack for the 0% body fat skinny road runner guys.

    Oh the packs I have tried b4 this one!

    • Familiarity: I've used it several times

    I have a Nathan pack that I love. I have been looking to add another to the rotation and have gone through m_a_n_y flavors. This one came across in a sale and I snagged it. I got the smaller one first - it is tiny and might hold 1.5 liter. I was wanting some that would hold 3 liter. This one is advertised to do such though I have not found a bladder that size that fits. It does hold a 2 liter nicely. This is a very comfortable pack. On my the pack is tighter the lower it goes. The straps over my shoulders are loose and not biding at all. The two cross straps allow for adjustment to make the fit even more perfect. Oddly enough there is not a place to easily stick the end of the host/bite piece. I had a magnetic attachment that fixed that. This is well made, light and enough stretch to fit snug yet without binding. I have a new friend!!

    The Best Running Vest

    • Familiarity: I've put it through the wringer

    I really do not like running vests or packs bur some ultra races require carrying some gear that does not fit into a waist pack. I tried different packs from various brands and none of them fit me well, or they had issues with bouncing. I tried this one and loved it immediately. It fit really well. I like that the "across the chest" straps are adjusted by changing the hole the strap goes into versus sliding on a rail (as the slider types always move). The pack does not have significantly storage but what it has works for me. I do find the small zippered pocket on the right shoulder strap to be somewhat useless except for things like pills, After purchasing it and using it as much as possible in 3 weeks, I used it for the Western States 100 and found it perfect. Overall, its a good pack, and ideal for me!

    Pretty Cool

    • Familiarity: I've used it several times

    I have a 17 inch torso and on the broad side in the chest and shoulders. I ordered the S/M and it does fit, although a bit on the tight side so I haven't used a hydration bladder with it. Marmot Kompressor Flasks work well in the front pockets and the main compartment has adequate room for a light jacket and trail food. If in doubt, I'd go a size up.

    Unanswered Question

    I am 6'1" 170lbs. My suit jacket size is 39 Long. I am lanky and thin but have broad shoulders. What size do I need? S/M or M/L? How should I exactly measure? Width across shoulder to shoulder or across armpit to armpit or across nipple line?

    Nice Ultra Running Pack!

    • Familiarity: I've used it once or twice and have initial impressions

    Familiarity: I've used it several times
    Just did 21 miles with 5k feet of elevation gain. I had 2L hydration bladder and room for food, fold up rain coat and .7 Adventure Medical first aid kit. The two front pockets can hold the Hydrapak 500ML soft bottles with ease. I put my iPhone 5 in the other front pocket which worked out well. Little bounce and never felt heavy even though the pack probably weighed about 8 pounds at the start of the run. Also the pack never got too hot and didn't get any hot spots. For reference I'm coming from the old UD Wasp pack which I thought bounced way too much. Can fit almost the same amount of stuff as the old Wasp pack.

    No bungee cord even though the loops are there.
    No whistle
    Some pockets are useless
    No hydration bladder tube holder so have to buy a magnetic one from Hydrapak.
    Straps could cinch tighter


    Great Running/Biking Vest

    • Familiarity: I've used it several times

    This vest was purchased for a forthcoming adventure race and although I have not used it yet for that I wanted to give my first impressions. I have used this for mountain biking and trail running upto 2 hours duration. I have also used it between 40-90 Deg heat. So far I have nothing but awesome things to say about it, no chaffing, no bounce, little thermal heat stress and very customisable. I have purchased UltrAspire Collapsible 500ml Bottle/Straw for the front pockets which work really well for hydration on the move. All in all I think this is vastly under-rated and compared to Nathan/UltrAspire/Salomon products is amazing value.

    Cannot reccomend it enough.

    Volcanic 50k

    • Familiarity: I've put it through the wringer

    Running was the poor man's sport until a few years ago. Now it's a fad and running events, shoes, and apparel are priced for the fashion minded yuppy. Fortunately, you have Mountain Hardwear which still makes moderately priced items like this race pack. It was one of the few that could be had for less that $100. I used it on a grueling 50k trail race that lasted 6+ hours instead of the usual 4 hours. Fits well, no bouncing around. I just don't understand why there are loops for a bungy system but no bungy system.