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REI Trail 40

rated 5 of 5 stars
photo: REI Trail 40 overnight pack (35-49l)

A great pack for lightweight and ultralight backpackers.


  • Plenty of pockets
  • Good hip pad and shoulder strap adjustment
  • Comfortable
  • Twin-zip design
  • Large exterior mesh pocket for damp items
  • Included rain cover
  • Integrated whistle
  • Integrated water bladder pocket


  • Relatively heavy compared with ultralight packs
  • Not enough compression straps

I originally purchased this bag to use as a daypack when hiking with my girlfriend. However, this was around the same time I started moving to ultralight hiking and now I use it for any kind of hiking / backpacking trip. I have only had this pack for about two months, but have already put over 250 miles on it with various loads.



I found the large REI Trail 40 to be a little bit on the small side (I'm 6'2"), but only slightly. The pack sits very comfortably, but the hip-belt is very slightly above where I would expect it to sit.  Still, the pack fits quite comfortably.


All in all, the Trail 40 has turned out to be a very comfortable bag. Once I got all the straps adjusted properly, it sat snuggly against my back without much shuffling. It doesn't breathe as well as a larger pack might, but the back is not nearly as complex, either.


The center pocket on this bag is 40L, which is plenty for day trip and actually enough for a multi-day trip if your gear is small enough. I have managed to fit all of my UL gear for a 3-day trip into this bag without lashing anything to the outside.

In addition to the main pocket, this bag has a zippered side pocket, one zippered top pocket, three mesh water bottle pockets (two of these are stacked on top of each other. Depending upon the size of your water bottle, you may be able to use both at once, or may have to choose one over the other.), one large mesh pocket over the main pocket, one mesh belt pocket, and one cloth belt pocket.

There are also multiple webbing straps for external gear attachment (including two ice axe loops).


This pack has a fair amount of organizational pockets. Inside the main compartment, there are two zip pockets on either side of the twin zippers and one on the central tongue. There is also an elastic pocket that covers the back of the pack. Also along the back wall, but separate from the inside of the main pocket is another pocket for use with a hydration bladder.

Between all these pockets, I have had no trouble organizing my supplies in such a way that I can easily access anything in the pack without needing to re-pack everything afterwards.


This may be one of the easiest packs to use of any I have ever owned. In most respects, no backpack is really difficult to use, but they do often require that you unpack a bit before you can reach something on the bottom or at the side. This is the first bag I have ever owned with the twin-zipper design, which completely gets rid of that issue.

The twin zipper design uses a large U-shaped zipper that runs the length of the pack. There are actually 4x zippers on this track. This allows you to open and close the bag  from any part of the track without opening the whole bag. It also allows you to completely open the bag (fold it nearly flat) for quick packing and organization.

When it comes to hydration, there is a pocket for a hydration bladder and loops / clips on the straps make it easy to attach a hose. However, I did find the side water bottle pockets to be difficult to reach without taking the pack off.  


  • Integrated whistle: A whistle is built into the chest strap on this bag. This is a nice touch if you're lost in the woods or find yourself facing an animal you'd rather not tangle with. 
  • Integrated rain-cover: I've always found pack covers to be about 60% effective, but it is nice to have one built in. Large mesh pockets make it easy to dry damp gear. 
  • Twin-Zipper design: The twin-zipper design has proven to have a number of benefits for me. First, it means I can quickly and easily access anything in any part of my pack, regardless of how overpacked it may be. Second, it allows me to fold the pack nearly flat and use it for extra insulation at night. I use a shorter-than-average mattress pad to save weight and place this bag (unzipped and folded flat) under my feet — it has proven to be a great insulator and unzipping it gives plenty of coverage!


The hip-belt and shoulder straps on this bag are on par with what I would expect from a larger backpacking pack. They allowed me to get a nearly perfect fit quickly and I haven't had to fiddle with it much since.

I do wish this pack had more compression straps. There are two straps that run vertically and allow you to pull down on the top pocket. This helps to compensate somewhat for a less-full pack, but a few horizontal straps would be better.  There are currently no horizontal compression straps. As it is right now, there is no way to compress the bottom of the pack if you only have a few items in it.


Granted I haven't had this pack very long, but so far everything seems really well built! My usual concern with outdoor gear is any mesh. I've had the most problems here in the past. So far, the mesh pockets on this bag have all held up wonderfully.

Source: bought it new
Price Paid: $99

This is the ideal multi-use travel pack at 40L with a panel opening, 8 exterior pockets, 3 interior pockets and hydration sleeve. It comes in both Men's and Women's and at a price of $110, it won't break the bank.


  • Full zip panel access
  • Carry-on size
  • Multiple pockets - front/top/side/hip
  • Tool attachment
  • Rain cover included

Overview: This is REI's latest all-around pack which replaces the Lookout 40 Pack. At 40 liters, it is big enough to carry a ton of gear but not so big that it can't be carried on a plane. The pack has tons of features to help with organization and the biggest change is the panel opening which makes accessing things in the pack much easier than a top-loading pack.

Personally, I find 40L is the sweet spot for capacity no matter what the activity, hiking/travel/climbing. 

  • Shape/Design: This pack has a traditional backpanel which means there is no gap between wearer’s back and the backpack. This makes the main compartment easy to pack and keeps the load close to the wearer's back. In comparison, a ventilated backpanel has a mesh backing allowing airflow behind the pack for breathability.

    The downside, however, is the shape of the main compartment becomes banana shaped making it hard to pack rigid items like a laptop or bear canister. Also, the load ends up farther away from the wearer's body. Personally, this tradeoff for keeping my back a little less sweaty is not worth it but some people do prefer it. If ventilated packs are your thing, these packs are in the same size range and also have panel access: Gregory Z38, Osprey Stratos 34 and Marmot Kompressor Verve 32/38.
  • Panel zip main compartment: This pack has a full zip panel so you can open just to top like a top-loader or open the pack fully to access all your gear.



  • 4 zippers for the main compartment: Allows for unzipping of the pack from top or bottom.


  • Front Pocket: One stretchy mesh zip front pocket which is good for a guide book or map.
  • Side Pocket: One side has TWO stretch pockets for tall bottles.


  • Side Pocket: The other side has a side pocket and vertical zip pocket.
  • Zippered top pocket
  • Top straps: Good for carrying a jacket or a rope :)
  • Interior sleeve: The sleeve is stretchy with bungee and fits a 15" laptop.
  • Interior pockets: There is a top mesh pocket with a key clip and a side mesh pocket.
  • The shoulder straps and hip belt are padded and there's an adjustable sternum strap with safety whistle. The padding is just right for a 40L pack and I image this pack can carry up to 40 pounds comfortably. Also, there are hip belt pockets which are always handy for keeping small items.
  • Hydration compatible: There is a slot for a hydration bladder that's outside of the main compartment. You can see the blue hanger that can be tucked away when not in use.
  • Included rain cover which stows in its own bottom zip pocket.
  • 2 straps on the bottom to attach a sleeping pad. These are not removable.
  • 2 daisy chains
  • Tool attachment: Metal tool holders for trekking poles and ice axe loops

Dislikes: None so far. The pack has all the features you need and nothing you don't. 

Recommended uses: Multi-day travel with the ability to pack a laptop, sport climbing, hiking, 1-2 day backpacking and any outdoor adventure. It's not big enough for a trad pack unless you carry the rope on the outside.

UPDATE - Packing for Climbing: I used this pack on a sport climbing day trip and took the following: 60 rope, harness, two pairs of climbing shoes, chalk bag, ATC, Grigri,10 quickdraws, Nalgene bottle, camera, camera lens. I was able to get all the gear in the main compartment of the pack with the rope on the bottom and the rest of the gear stacked on top. The pack was comfortable to carry though my approach was about 15 minutes so i wasn't carrying it for very long. 

Two comments after the day. 1) The pack is a small 40 liters. It fit the gear with no room to spare but i could also fit the same gear in an my old REI Talus 35. I also tried backing into my Mountain Hardware Splitter pack (35?38? liter) and had room to spare. 2) The bottom of the pack has a roundish shape. I prefer packs that have a flat bottom allowing them to stand up upright. This isn't a huge complaint, but I often stand the pack up while packing or accessing gear. 


Notice the pack is laying down... i couldn't get it to stand for the picture. 

very comfy carry

Source: bought it new
Price Paid: $109

Great carry on travel size, pretty much the max that most airlines will take. Easy access to main compartment. Comfortable.


  • Great size
  • Main zipper system provides easy access
  • Zipper system also allows top loading to compress the load if I need to stuff it full
  • Hydration pocket makes a nice computer pocket
  • Other pockets are handy and good size
  • Sleek narrow design makes walking through crowds easy
  • Trekking pole attachment points


  • Waistband straps are absurdly long (this is nitpicking, I'll cut them to size)
  • There appears to be no way to put skis on the sides, which would be a nice addition for backcountry skiing

I just bought this pack for a trip to Europe. We are on the trip now and I'm very happy with this as a travel pack. I feel that is an optimum size. I was able to pack in this as a carryon for a three-week trip that includes a weeklong bike trip, so normal spring/summer travel clothes, plus two bike kits, bike shoes, gloves, arm warmers, shell (no helmet, pedals or bike packs).

I use the hydration pocket as a computer pocket for my MS Surface, so it is very easy to get out the computer on a flight. I like this size because it is also small enough to use as a day pack when going for a hike or to the beach.

The zipper is a four-way zip, so you can get in the sides, open completely or load from the top. So after you get everything in from the top/sides, you can compress from the top.  

There are two top pockets—one accessible from the outside and one from the inside. There are also side mesh pockets for water bottles, energy bars, or other stuff you may want during a hike or ski. It's nice to keep those empty when walking through airports so the pack is narrow for walking through crowded areas.

Source: bought it new
Price Paid: ~$80

Awesome, affordable, versatile, and tough.


  • Versatile
  • Light
  • Tough


  • Lacks detachable lid/brain

This is an awesome and very versatile pack. I took it into the Washington Enchantments in 11/2018 and couldn't be more pleased.

I was in the military for a number of years. During that time I learned to live out of a pack frequently and for extended periods of time. Probably the best weekend pack I could ask for.

The only improvement I would ask for is a detachable "brain" or lid. It would allow JUST enough extra space for the little things while allowing a top strap down on top of that as well as under (for a rope specifically if I have to use the top tie downs for something else). But, in all reality I feel like that "improvement request" is even grasping at straws.

I've used this as an international travel bag/carry-on as well as a backcountry pack. It fits in an overhead bin just fine and I could easily fit 3-4 days worth of extra clothes and a toiletry kit as well (not to mention snacks, reading, extras, etc.).

When using it in the backcountry, I also found that it does a good job keeping "tight." Once I get everything settled and cinched in for a long hard haul, nothing moves out of place until I move it.


Backcountry and international travel

Source: bought it new

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Price Current Retail: $149.00
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Reviewers Paid: $80.00-$109.00
Price Current Retail: $149.00
Historic Range: $46.93-$149.00
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