Review of REI Co-op Flash 18 Daypack

REI Flash 18

Credit: M.Swigart

Last Updated on April 28, 2021

The REI Co-op Flash 18 daypack is a go-to for extreme outdoor sport enthusiasts. The simple design, light weight, and affordable price makes the pack a customer favorite. Though it has its weaknesses, I’ve found this pack to be beneficial on multiple occasions. I’ve had mine for over three years and it is still my go-to for outdoor or day to day use. Check out the pros and cons, as well as the features below to decide if this pack is the right one for you.

Highlighted Features of REI Co-op Flash 18


Ripstop Nylon makes up the Flash 18 daypack from REI. What is nice about Ripstop Nylon is its lightweight characteristics while still being durable.  The material of the Flash 18 is strong and protects from rips in the pack, but it is not waterproof. In the case of a storm, I simply place my rain jacket over the pack to keep the pack and contents dry.

Black REI Flash 18 daypack

Credit: M. Swigart


This backpack has a minimalistic design. It can easily fit into large packs, but also has a daisy loop to offer the option of external attachments.  The pack has one large pocket and a drawstring opening. Inside the pack is a small zipper pocket and area for a water bladder. The necessity of taking off the pack to retrieve gear in the pocket can get annoying, but the simplicity of the design allows the pack to be lightweight and travel friendly.


The Flash 18 is a smaller daypack at only 18L, but its size works well with the pack’s design.  As a lightweight option to hold a few items, the Flash 18 is a good choice.


If you are looking for a lightweight day pack, the REI Co-op Flash 18 was designed for you. This pack weights only 10 oz, which is on the lighter side of daypacks. There are daypacks available that are simply thin material which lends to being ultra-light, however the benefit of the Flash 18 is its thin foam back-pad and cushioned material for the shoulder straps. For the extra details, while still offering a lightweight pack, this daypack is a good choice for adventures that require light gear.


REI’s Co-op provides a small back panel that helps to cushion the load. The back panel can also act seat cushion if contents are removed from the pack. When it is not packed with a heavy load, or with pointy objects, the Flash 18 can sit comfortably on your back. But, due to the simple design and lack of cushion or frame, this daypack can be uncomfortable to wear if over packed. The main problem I run into is feeling my gear through the pack. This is not a difficult problem to fix if I pack minimally and arrange objects to sit on my back smoothly.

REI Co-op Flash 18 Daypack

Credit: M. Swigart


To follow the pattern of the Flash 18’s minimal design, it also has little ventilation. However, if packed light, this pack does not need much ventilation to still be comfortable. The shoulder straps also provide ventilation and cushion to help prevent sweaty armpits and sore shoulders.

REI Flash 18 co op

Credit: M. Swigart


The simple design of the Flash 18 slightly hinders its functionality. While having only one main compartment and one small zippered pocket is helpful for rock climbing, mountain biking, or possibly even running (if you do not mind some movement), the design can be annoying for other uses. Snacks and water bottles sit loosely in the main pocket, which is not easily accessible on the go. REI considered the need for easy access to water and provided a space of a 3L water bladder to sit inside the pack as well as an opening for the straw.  The Flash 18 also includes a daisy chain to attach items that you want to keep accessible.

Once all loaded up, a hip belt and sternum strap help to hold the pack tightly into place. I rarely use these straps as the pack fits comfortably without extra securing. However, for more extreme outdoor activities these accessories would come in handy. 


  • Light weight
  • Breathable stretch-mesh shoulder straps
  • Padded back panel
  • Detachable hip belt and sternum strap
  • Capable of holding a hydration pack
  • Interior zipper pocket included
  • Daisy Chain allows for easy attachment of external gear
  • Affordable


  • May feel uncomfortable when holding a large amount of weight
  • No external pockets of water bottle holders
  • Non-waterproof
  • No back frame and minimal cushion

Final Thoughts

The REI Co-op Flash 18  is the definition of a multi-use daypack. So much so, that my husband and I often debate who gets to use the REI pack for day treks. We prefer the simple style, light weight, and comfortable feel of the REI Co-op pack. If you are looking for a simple, durable pack to comfortably carry a small load, the Flash 18 is a good choice.

Check Out Other Gear Reviews By M. Swigart:

About the author

Mariah Swigart

Mariah Swigart is often found camping, climbing, hiking, and kayaking in her home state of Arizona. She loves exploring new locations for her outdoor hobbies, and believes each trip is an opportunity to try a new piece of outdoor gear. Check out to read about her most recent adventures.

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