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REI Co-op Flash 18 Backpack Long Term Review

Aaron Zagrodnick



With a market full of competitors, choosing the right daypack for your needs can be a difficult task. In this review, I’ll evaluate the features and performance of the smallest pack in the popular REI Flash series – the Flash 18 (18 = 18 liters / 1100 cubic inches). In a sea of competing daypacks this is one pack that has managed to stand out for the past decade plus, partly due to its competitive price point. However, with an attractive price I of course always have my concerns – sometimes in the backpacking world budget priced gear can often result in a solution much heavier than competing products and lacking in features that you may find yourself longing for down the road.

REI Co-op Flash 18 Backpack Long Term Review

The REI Co-op Flash 18 backpack is a minimalist, lightweight daypack that has proven to be reliable over the years.

Flash 18 Features

Personally, I hate excess gear. Don't get me wrong – while I love cool stuff as much as the next person – if I could own one pack that will get me through every situation, that's the way I'm going to lean. At least at first. I tried this out for a while, until one day many years ago when I found myself lugging around a pack designed to carry 10 days of supplies to my favorite Saturday getaway. It became apparent that gear can't always be viewed in black and white terms. My pack was woefully empty, stays and load lifters there yet serving no purpose. It felt like I was using a semi-truck to bring home a few flower pots. I needed something clean, cheap, and functional. Plus…I gave myself a great excuse to try out some new gear. So after hitting the local REI, I walked out with a Flash 18, which has been a frequent companion since that time. Over the years REI has released incremental updates and changes to the Flash 18, however the baseline has remained mostly the same: 18 liters of top-loading storage, lightweight hip belt, shoulder, and chest straps, and an overall minimalist design. In this review we'll look at the basic design of the pack and how it has worked for more than the past decade.

Once I got my hands on the Flash 18, the tags came off and the pack hit the digital scale. REI listed the pack at 11 oz and my pack met this mark exactly. This is a bit heavier than the original version of the Flash 18 – which while listed at 10 oz, came in under spec at 9.3 oz. The pack is extremely simple and clean, with just one small exterior pocket on the latest version. A twin row of webbing daisy chains run the length of the exterior, with one larger "tool loop" at one bottom corner. These don't offer many options for carrying gear outside the pack without some ingenuity, but with a small time investment they can be used to greatly add to the usability of the pack. The newer versions of the pack have done away with the rows of daisy chains and instead use 4 loops to allow securing additional gear. Whether this is an upgrade or downgrade is up to personal preference.

Rei Co-op Flash 18 Backpack

The pack is top loading, and in addition to the large interior compartment you'll find 3 additional pockets. The hydration pouch is found along the back panel, with a small loop sewn into the top should you wish to secure the top of your hydration reservoir to prevent sagging when low on water. The hydration pouch itself easily accommodates a 3 liter Platypus Hoser. Above and centered between each top shoulder strap attachment point, a weather-shielded opening for your hydration hose can be found. The pack has a padded back panel that's removable, (doubling as a sit pad according to REI) so behind the hydration sleeve you'll find the back panel pad compartment. The compartment closes to secure the pad using a thin hook and loop closure. The pad itself is quite thin measuring only 5 millimeters thick, and at .3 oz, is very light. REI has included a zippered pocket on the Flash 18 (great for keys) for some time, originally on the inside but most recently, and perhaps more conveniently, this is now located on the side of the pack.

REI Flash 18 Hydration and Closure

A drawstring closure is used to close the main compartment, and a small flap covers the opening when cinched. This isn't weatherproof by any means, but if used with a pack liner you should be set for rainy conditions. A slider allows you to easily close and loosen the top drawstring.

The hip belt utilizes 1” webbing, with ¾” in use for the sternum strap. Each strap closes using conventional plastic buckles. The sternum strap buckle also features a convenient whistle, and the sternum strap height is adjustable. The sternum strap and hip belt can both be quickly and easily removed if desired, which will shave off 1.9 oz. Shoulder straps use a different material – relying on lightweight honeycomb nylon mesh that adds a very small amount of perceived cushioning. The ventilation of the mesh is excellent, and serves well to keep the wearer cool in hot weather.

The pack body itself is constructed of 70-denier ripstop nylon, of which you have several colors to choose from. This fabric has a much heavier feel than silnylon, but is still quite lightweight. Starting with the 2nd generation Flash 18, REI began enhancing the pack with water resistant fabrics. Currently, the pack utilizes a nonfluorinated durable water repellent (DWR) finish. In practice I found that water would not penetrate the fabric, but water is still able to penetrate the seams. The fabric is able to withstand moderate abuse, and you may need to be careful hiking with the pack in rocky areas or off-trail where you might encounter a few tree limbs reaching out to snag the fabric.

Flash 18 on the Trail

The usability of this pack is excellent – with one caveat. Since the simple and elegant approach that REI took with this pack eliminates all outside pockets that can hold a water bottle for drinking on the move – I found that hydration system users should be quite satisfied. If you prefer a bottle approach and won't be able to adapt to a hydration system for use with this pack, you may walk away unhappy and the addition of at least one side pocket to hold a water bottle or two would have been appreciated by many users. On the other hand, one outing with the pack involved a day trip fly fishing for 8 hours along a local stream. The pack easily swallowed breakfast and lunch, leaving plenty of room for photography and rain gear. The slim profile allowed for a complete range of motion as I snuck through the streamside brush and dipped under fallen trees – something outside pockets may have hindered.

REI Flash 18 on the Trail

When turned inside out the Flash makes a stuff sack for longer expeditions – allowing for a summit pack or daypack to range with from base camp when needed. However, at about 11 oz, the Flash makes a heavy stuff sack. If you're simply looking for a daypack to take along with you on longer trips to explore away from base camp, lighter options exist.

Additionally, the removable back pad panel doubles as a sit pad according to REI, but I found the pad to be on the small side for this type of use. Since it's so thin, it also doesn't really add any cushioning and durability is a concern – I had several holes in the pad just from the first use. I was hoping that the foam back panel might add a bit of rigidity, perhaps forming a frame of sorts allowing us to stretch the comfortable carrying limit of the pack, but it's quite floppy and doesn't really add any structure. If you're using the pack without a hydration reservoir, you might find that the panel takes the edge of any sharp or pointy objects contained within the pack, but when used with a hydration system the reservoir itself served that purpose for us and I left the pad at home.

At this point it should be safe to say that the Flash 18 is an admirable day hike performer, but can its limits be stretched? Absolutely. For just a few dollars, a 5 minute time investment, and less than a 1 ounce weight penalty a shock cord system can be added to the outside of the pack to greatly increase its “range”. Here I'm using about 8’ of 1/8” shock cord and one properly sized cord lock. This allows you to carry whatever you please and should enable most ultralight packers to easily use this pack on mild 3-season overnight trips and possibly longer, simply depending on how light you pack and how much you gear you can manage to carry outside of the pack. The latest models have unfortunately gone away from using the daisy chain but external bungees could still be added to the four loops that are in their place.

REI Gear Flash 18 Backpack

The REI Co-op Flash 18 backpack fully ready for an overnight jaunt with gear, water, and food

How does the pack carry? Quite well assuming you don't push its limits. I was generally comfortable packing weights up to about 15 pounds. Up to about 20 pounds the pack was manageable but comfort began to suffer. The minimalist hip belt is actually able to perform some load transfer when the pack is tightly packed, or when a sleeping pad (of thicker and denser foam than the included panel) is used internally to create a virtual frame. However, above the 15 pound mark the hip belt became unable to offer any type of noticeable load transfer to the wearer's hips. Some users may wish to remove the hip belt and sternum straps to lighten the pack even further, but I found them critical not only for carrying loads comfortably as just described, but also for securing the pack tightly when engaging in highly mobile activities like off trail hiking or mountain biking.

Per the REI specs, this pack fits torsos in the 15-21” range and with a hip belt range of 26-42 inches. I was able to push the pack with a longer torso comfortably at the low to mid weight ranges, but if you'd like to push to weight limits of this pack longer torsos should shy away. At the higher weight ranges, tightening of the shoulder straps becomes necessary, raising the hip belt uncomfortably high for longer torso users. Hopefully, REI will release multiple sizes in the future.

REI Flash 18 Daypack

While the REI Flash 18 offers great features, it is only available in one size, and for those with longer torsos, a larger size (although not currently offered) would be ideal.

Comparison to Earlier and Later Models

As you would expect, the price of the Flash 18 has gone up over the years, and REI had implemented quite a few changes along the way. The pack is currently listed at $49.95. The first model was listed at 10 oz, but came in impressively under-spec at 9.3 oz. The weight of my pack from 2012 tested at 11 oz, and the newest pack is listed at 9.5 oz. All versions of the Flash 18 allow customization that can get the weight down even lower, but you'll have to lose the functionality of the chest strap, hip belt, and foam back panel to make that happen. The shoulder straps are slightly wider than the first generation and are woven into a honeycomb pattern that offers a bit of padding, and I did find this pack more comfortable and stable on the shoulders than the earliest versions.

The closure system was updated with a slider buckle, and the entire system was easier to understand than before. However, I found that the older version was easier to open and close in a single motion. Also, a loop has been added above the hydration sleeve – clip your reservoir in here if you want to prevent sagging as you drink.

The foam back panel and matching sleeve using a Velcro closure were added, and the interior pocket system has been improved. The 2nd generation's interior pockets were on the opposite side of the hydration sleeve and included one larger sized but zippered pocket that sat near the top of the pack. For extra security, it also had a ribbon and clip that sat within the pocket for your keychain or other valuable items. The current models have two interior slip pockets on the same side as the hydration sleeve, while there is an added exterior zipper pocket. This newer version's zippered pocket is located on one side of the pack, allowing phones or snacks to be more accessible while hiking while keeping a sleek profile.

REI Co-op Flash 18

The REI Flash 18 backpack features a ripstop nylon fabric that is treated to repel water.


Overall REI has it right with this pack. Simple value. Currently retailing for about $50, you'll be hard pressed to find a pack in this category, this well built, for a better price. Granted, there are a few drawbacks, but they are workable drawbacks and don't apply to every user's style. REI has added some features over the years, but luckily the Flash 18 has remained a true minimalist daypack. I feel that the best part of the Flash 18 feature set lies in its low price and simplicity. However, it's hard to complain about this much usability at such a great price.

The REI Co-op Flash 18 backpack retails for around $50. You can find it here at REI. For a little more capacity, a top lid, and side pockets, the Flash 22 daypack is also worth a look. You can additionally view REI's full selection of daypacks here.

Editor's Note: This article originally appeared in the first issue of TrailGroove Magazine. You can read the magazine article here, which features additional photos, as well as our REI Flash 18 rating, pros and cons, and more.



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