Gear Review: Ultimate Direction Fastpack 35 and 45

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In the same way that many hikers and backpackers have adopted trail running shoes as the de facto best choice for most three season hiking, trail running vests and backpacks are starting to gain mass adoption as well. Much like the switch from boot to trail shoe, a switch from a structured backpack to a running vest provides added comfort, improved fit, and better functionality for fast and long days on the trail.

The main issue with most trail running vests is that they don’t usually come with more than 15 liters of storage volume. A few years ago, Ultimate Direction changed that by combining running vest comfort with backpacking capacity for their Fastpack 20 and 30. Ultimate Direction is best know for their running vests and hydration products that are used by some of the world’s elite ultra runners.  This year, Ultimate Direction has released a revamped lineup of packs they’re calling the Trail Collection. This includes the Fastpack 15, 25, 35, and 45. For this review, I’ll be taking a look at the 35 and 45.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking

The Fastpack 35 and Fastpack 45 differ in volume and color only. The function, features, and performance have proven to be identical in my field tests, which is why I’m reviewing them together. I’ve used the Fastpack 35 for almost every hike I’ve been on in the last few months, and I’ve used the Fastpack 45 on a few overnight outings. Long story short, these packs are phenomenal and have moved to the top of my recommendation list. I do have one or two nit-picks though. I’ll get into all of that and more in the following review.

The Fastpack 35 retails for $184.95 and the Fastpack 45 retails for $199.95.

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Build, Design, And Functionality

Storage, Size, Materials, And Weight

The Ultimate Direction Fastpack 35 and 45 are listed at 35 liters and 45 liters, respectively. I have both packs in a size M/L, which makes the actual pack volume a few liters more than the listed amount. The Fastpacks use a roll top closure which makes them feel even more spacious. The size M/L is made to fit a 30-50in chest. I have a 42in chest and a 30in waist, and the Fastpacks feel like they were made custom for my frame. There is lots of strap room in both directions though, so I’m sure they will fit a wide range of bodies. The Fastpack 35 comes in at just over 26oz and the 45 weighs about an once more.

The Fastpacks do not have a frame, but they do have a foam back pad that provides structure and comfort. The back pad is removable. Just lift up the Velcro tabs above the internal hydration sleeve and the pad can be pulled out.

For day trips and overnight backpacking outings, I’ve had no trouble fitting all of my essentials. For trips requiring a bear canister, things can be a bit tricky, as the Garcia and BV500 will only fit vertically. Longer tent poles can also be an issue if you’re used to a pack that an carry them on the inside. I always carry my poles on the outsole, and have done the same with the Fastpack 45. Family outings with my Big Agnes Copper Spur HV UL3 have been a joy.

The pack dimensions are 27.6″ x 11″ x 11″. I’m 5’11”, and the Fastacks sit comfortably on my hips without any sag or chaffing on my glutes. The bodies of the Fastpacks are made out of 100D Robic Triple-Ripstop nylon that has proven to be very durable and water resistant. The pockets and back panel are made of a “Power Span Stretch Mesh”, and the shoulder straps are made of a “MonoRip Mesh”. I’ll get into this more in the Pockets and Shoulder Straps sections below.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking


The straps and customization options on the Fastpacks are pretty minimal, but functional. The roll top closure buckle connects with the side compression straps that run under the side pockets. With only two straps, you’re able to both vertically and horizontal compress the Fastpacks. This is what makes the Fastpack 35 so versatile for hiking. I can go super light with just water, or I can throw in a bunch of layers and nutrition without have to work hard to dial things in. Whether the pack is empty or full, it always seems to ride evenly and without a lot of shake or wobble. The one exception to this is when I have 1L bottles in the side pockets with an empty pack. Since the base of the pack has no frame or structure, the bottles can jump around quite a bit while running or moving fast.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking


The Fastpack 35 and 45 have a hydration sleeve in the pack for those that like to carry a bladder within the pack. There is a dual button clip to keep the bladder from bunching at the bottom of the sleeve. There is a central split port to pull the bladder tube through to the front of the pack.

*You can see a Velcro tab just above the blue line in the photo below. If you pull up on this, you can access the foam back pad.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking


The Fastpack pockets are my favorite feature of these packs. They have proven to be functional and versatile. They’re made of “Power Span Stretch Mesh”, that allows me to fit oddly shaped items into each pocket and still provide a secure fit. As a “photography first” hiker, bringing my camera along is very important to me. This is the first pack that I’ve used that allows me to carry my camera on my chest without any additional attachments. I can even do this with my Sony 10-18mm! This is a real game changer for me. I no longer have to pick a lens based on how easy it is to carry. I also rarely miss a shot with my camera being so easy to access.

As I mentioned above, I use water bottles for hydration instead of an internal bladder. For those that like to carry the bottles on your chest, there is a stretch pocket on your right shoulder. The major gripe I have with the pockets on the Fastpacks is that the chest pockets are not symmetrical. There is no stretch pocket on the left shoulder, just a large zipper pocket with a sleeve behind it. The nice thing is that the zipper is waterproof, so you can carry a map or sensitive electronics. You can jam a bottle into that pocket if you want, too, but it’s not very comfortable. This isn’t a huge issue for me, as I prefer to cary 1L bottles in each side pocket. The side pockets are easy to reach, and this is one of the only packs where I can easily grab a bottle and put it back in without going through contortions.


A “MonoRip Mesh” is used on the shoulder straps of the Fastpacks which makes for a comfortable and pinch free ride. The flat shoulder straps sit along the shape of my traps quite nice. Ridged straps on standard backpacks have always caused me discomfort here. Not so with these vest style packs. The coolest part of the shoulder straps is that they’re part of the “lnfiKnit” mesh panel. This is essentially once piece of fabric that makes up the back panel and shoulder straps. I have experienced no chaffing, and on most days forget that I’m wearing a pack. Each vest shoulder strap has a strap that pulls back under the arm more than it pulls down. This provides a nice “hug like” fit.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking

There are two chest straps on guide-rails that connect with a buckle. Having the straps on guide rails really helps dial in the fit. The waist belt has a larger buckle, and the belt has not additional pockets or storage. While hiking, I usually leave the removable waist buckle undone, and only use it when I want to keep my pack from moving side to side. All three straps work very well to dial in the perfect fit.

One thing to keep in mind is that there are no load lifters on the shoulder straps of the Fastpacks. This is important if you plan on carrying a heavy load. I found that the max weight I could comfortably shoulder in these packs was around 20lbs. Anything north of 20lbs, and I would get that dull ache in my back and shoulders that every hiker and backpacker will be familiar with. These are fastpacks though, and not built with heavy loads in mind, so I can’t be too critical of a dog that can’t fly. Having said that, my Salomon hydration packs do use light load lifters that I have found to be effective on the rare days when my pack is weighed down.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking


As I mentioned above the “lnfiKnit” mesh panel is one piece of fabric that makes up the shoulder straps and back panel. This fabric breathes and dries very well.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking

Pole Attachment

The Fastpacks have trekking pole attachment bungies on the back of the pack for days when you want to move with free hands.


Day Hiking

To me, this is the ideal use for the Fastpack series. These packs excel on peak bagging ascents, 20 mile day hikes, or monsters like Rim to Rim hikes of the Grand Canyon. I can’t really think of any day hike these packs wouldn’t be perfect for. I’ve used the Fastpack 35 on many hikes in the last few months short and long. I’m able to carry all of the water I need, food, layers, and camera gear, or go super light with just water.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking

Overnight Backpacking

As much as I love this pack for hiking, it’s name is actually “Fastpack”. Fastpacking is the combination of backpacking, fast hiking, and running. The goal is to carry only the essentials for the lightest pack possible (Sage to Summit has a nice write up on fastpacking if you’d like to read more). On top of the peak bagging and day hiking functionality of these packs, they’re also perfect for fastpacking or short backpacking trips. As I mentioned above, the only two drawbacks are the lack of load lifters and the awkward fit of a bear canister. I’ve been able to fit two quilts, a 3P tent, two sleeping pads, food, toiletries, and stuff for my dogs quite comfortably.

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking

Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking

Likes And Dislikes

If you’re looking for a lightweight backpack that has the comfort of a running vest but with more volume, you can’t go wrong with the Ultimate Direction Fastpack Trail Collection. You can tell that these packs are designed by and for athletes that log serious miles in the mountains. I’ve put quite a few miles on my Fastpack 35 in the last few months, and it will be my go to pack for just about every summer outing.


  • Comfort and fit
  • Pocket versatility
  • Size and compression
  • Breathes and dries well


  • Lack of load lifters with heavier loads
  • Asymmetrical shoulder pocket design

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Gear Review Ultimate Direction Fastpack 35 and 45 Backpacking Hiking


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35 thoughts on “Gear Review: Ultimate Direction Fastpack 35 and 45”

  1. Nice review. I’m looking at the Fastpack 45 for a 250km solo loop run/hike later in the year. How have you found the water resistance of the packs – is a pack cover required for inclement weather?

    • The Fastpack 45 would be a good choice. The fabrics used are listed as “hydrophobic”, but not waterproof. The zippers are waterproof. Living in Southern California, I don’t get to test my gear in a lot of rain. I did get to hike in a few drizzles though, and the 45 stayed nice and dry. For longer days in the rain with heavy and sustained downpours, you’ll probably want pack cover.

  2. Hey Drew, thanks for great detailed review! I’m pretty sure you’re the first who reviewed these two packs =) I’ve bough both packs — the 35 and 45 — a week ago just to understand which of them would work best for my needs. Now I’m in trouble choosing which to send back as I liked both very much 🙂
    What do you think about the waist belts on these pack? I haven’t noticed any help with weight distribution between shoulders and hips (load was 19lbs). Seems like waist belt is onto to keep the pack closer to body.

    • Hey Max. Thanks for reading. The waist belts are more for security of fit. I like to hike uphill and run downhill. The waist straps really help to prevent my pack from moving side to side. Like you say, they don’t provide much assistance in distributing weight to the hips.

        • It might be for comfort of fit and expected loads. The 35 just has the belt attached to a daisy chain. The 45 has more of a hip belt style with webbing that wraps around the side of the waist. Because of this, the 45 transfers a little more weight onto the hips. I’m sure they’re thinking is that anyone buying the 45L pack will want/need the hip belt, whereas the 35L might be used more as a day hiking or adventure running pack. And of course for product differentiation aside from just color 🙂

  3. Probably you are right. But since I could not felt any help with transferring weight onto the hips — with both the 35 and 45 — I was thinking if there’s any other benefit of having non-removable belt on the 45 =) The belt on the 35 gives you more options in terms of what to do with it if you don’t need it (remove completely or wrap it around the pack and buckle on the pack’s front).
    Anyhow, I’m going to test both of them in Yosemite in 2 weeks. My current mindset is that the 45 should work great for more than one overnights and it also fit bear canister well. I want to find out if the 35 can do the same, otherwise I’ll go for UD 25 or 30 model for a day hiking option (I mean 35 is big for a day hike IMHO).

    • I agree, the 35 allows for more flexibility. That’s probably why I’ve been using it 80% of the time. The 45 is when I need to pack enough for me, my partner, and our son. Let me know how your testing goes in Yosemite!

      • Hey Drew, so the 45 did almost perfect in Yosemite. ‘Almost’ because with 23 pounds it felt noticeably annoying for my shoulders after 5 hours of hike. The possible reason is the shoulder straps which tend to wrinkle on top of the shoulders creating a hot spots. Probably a sizing issue but I’ve tried both sizes and got the same issue with both. It wasn’t a drama at all, just some redness on my skin and fatigue you can develop with almost any backpack out there.

        Another issue I’ve found was with the bottom part of the daisy chain: when you put the pack on the ground or on the rocks it began to wear out unbelievably quickly. So after 3 day hike it looks like it is about to fall apart. I can see numerous rips on it.
        That’s it for the cons.

        – base weight of the pack!
        – amazing front pockets. I was able to put literally everything I need during a hike in those pockets — snacks, delorme, iphone, 750ml smartwater bottle, sunscreen, bug repellent, knife — and if my fellow hiker haven’t been so hungry all the time I wouldn’t had to stop to get the bear canister from the pack (I was awarded to carry our shared bear can).
        – huge thus great side pockets! 2 smart water bottle in one pocket + filter + a bunch of other stuff and the mesh is super strong (comparing to the mesh on my osprey atmos 65). BTW all materials used for this pack (except the daisy chain) feel very durable.
        – compression straps — amazing! I was able to make the pack to be ‘fit’ and nice on my back, I haven’t experienced any bouncing and balancing issues with this narrow profile pack.
        – I was using BV450 bear can and put it on its side so the flat lid was against my back which was super comfortable. This size of the bear can was easy it get in and out.
        – the waist (hip?) belt. I cannot say anything bad about it. It definitely kept the pack close to my torso greatly and I haven’t experienced any bouncing. Not sure if it provides any weight distribution though.
        – the two sternum straps worked very good. I liked that depending on the conditions — climbing up, crawling downhill or running — I was able to change their positions which provided me more comfort. I mean 2 sternum straps work better that one strap in a regular pack.
        – the foam back panel is easy accessible and I was happy to use it to sit on rocks and ground. I’m sure it can be used as an emergency sleeping pad too.

        In overall I like the pack. I believe there’s some room to improve the sizing to achieve more comfort with the shoulder straps. Probably the load lifters you’ve mentioned in your review would also help in this sense.
        At the moment I’m going to fix the issue by switching to the 35. Smaller pack — less stuff you can squeeze in =) The only issue is a bear canister (BV450 won’t fit the 35 so nicely as the 45) so I’m going to pick the smallest can available at the moment.

        Thanks for reading!

        — Max

  4. Hi, I noticed you reviewed this bag and the exos 48. Im trying to decide between the fastpack 45 and osprey exos 48. Im considering using it for a 5 day through hike (and hopefully many more). I haven’t dialed down my base weight yet, currently its at 23 lbs. I’m not fastpacking, just regular backpacking but I liked the idea of using the fastpack because of its lighter weight and I like how it looks more. On the other hand I like the osprey’s hip belt and the fact that it is more a traditional backpack. Which one would you recommend between these 2?

  5. Great review Drew. Am going on a 2.5 weeks multiday self support race. Total weight will be about 22 pounds. Not sure if you have tested the Fastpack 35 with such weight and how’s the comfort level?

  6. Thanks for the review. Good stuff. I’m doing a hut to hut run/hike in the alps in August from Chamonix to Zermatt, shooting to do it in 8 days. Did a similar run last year and went super light with the Osprey Duro-15 and suffered some after hitting a summer snow storm on a high col without the right gear. Won’t make that mistake again. Would you take the 25 (10 bigger than what I had last year) or the 35? Thanks in advance-

  7. Hi, would you recommend the 25, 30 or 35 l bag for walking the Camino de Santiago? And will the pressure on the shoulders instead of the waist really not matter on the camino? I am just wondering 🙂

    • The Fastpack comes in 15, 25, 35, and 45 liter options. I would go with the 35 since the 15 and 25 don’t come with a hip belt. The hip belt doesn’t add much support, but it’s better than not having one. 35 is also a comfortable amount of storage that won’t require you to worry about volume. The difference between the 25 and 35 is 155g (5.5oz), but at 710g, the 35 is still a very light pack when compared to traditional backpacks.

      As for the pressure on your shoulders and the fact that there are no load lifters, it is hard to say. It will really depend on your base weight. I carry camera gear, so my pack tends to be a little more heavy these days. I opted for the Osprey Levity on the Portuguese Route this summer. It was a phenomenal lightweight pack.

      • Thank you for the answer! It helps. I have around 5-7 kg with me. So I don’t know if you have a feeling about that being too much? The Osprey Levity is 45 sounds big, but you felt it was perfect?

        • 7kg is reaching the limit of a comfortable load for me with the Fastpack. 5kg would be a better target for a long walk like the Camino. The Levity is .8 kg, so although it is high volume, is very light. For me, I loved the way it felt. It is a very comfortable pack for long and short trips. I prefer the Fastpack for hikes where I run a bit here at home, but for the Camino, the Levity was perfect.

      • Thanks Dew for this helpful review and the above mentioned comment on Christopher Beirne’ question. I am struggling with the same question, multi-days running (incl. sleeping gear etc..) with the FP 25 or 35? Surely both packs are very comfortable. Probably the hip belt will make the difference when running downhill and the pack starts inevitably bouncing around.
        Btw, love your travel adventures. Very inspiring!

  8. Hi Drew. Hope you’re still here. In order to carry it in a larger main pack for summit treks from basecamps, how small does this fold fold down when empty? Do you know? Thanks.

  9. Thanks, and completely agree. Love my Fastpack 35, but it has limitations. Namely, it cannot carry weight because of the lack of load lifters. While, most my adventures are only a few days out while “fastpacking”, I cover dozens of miles per day, and when in the desert need to carry water (which is heavy). So I am on the search for something that has about 40 volume and can comfortably carry 30lbs


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