First impressions: Sierra Designs Flex Capacitor

Note: This article is not a review of the Sierra Designs Flex Capacitor.  I am writing just some initial impressions after a weekend of use. A thorough review of gear takes at least one season, preferably two seasons, of good use. 


Flex Capacitor on West Buffalo Peak

Andrew and I have known each other for quite a few years now.

We knew of each other through mutual friends in common, saw each other at various events, spent time together as I assisted him with his guiding and formed a friendship as we’ve talked about our lives outside of the outdoors..especially on some early-morning drives to the trailhead!

In some ways our lives have followed a similar arc.

We grew up within twenty miles of each other, spent a good chunk of our twenties exploring the backcountry of the United States and then settled into a different life in our thirties.

Andrew’s routes are more pioneering than mine, of course. And I dabble in a part-time outdoor career while Andrew has managed to make a livelihood out of his passion for the outdoors.

But we are both at the stage in our lives where multi-month trips on the long trails is not a priority.   Our trips tend to be a little off the beaten path. What we bring and use for gear and clothing on these trips has evolved to meet these requirements.

We both have a similar outlook from these experiences, too: The sub-1lb packs and similar gear  loved by long distance hikers on the well-known trails are a niche item. Something made to suit a specific purpose. A purpose not necessarily meeting the needs of most people and their activity in the outdoors.

On some of those early morning drives to our guided trips, we discussed how there is a niche for lighter weight gear that is durable, versatile and not overly expensive. Something that a time-strapped person can use for a variety of purposes without putting a huge dent in the wallet.

Bread and butter gear in other words.

Equipment that works for a quick over-nighter in the Indians Peaks Wilderness in summer covers a person for a long weekend in the fall and can easily be put into use when the rare two-week block of time comes up that can be devoted to backpacking.

Most people do not have the time, space or money to have multiple packs, shelters or pads to cover many different situations.

One pack. One shelter. One pad. One sleeping bag or quilt.

And all this gear needs to work for three-season conditions and even into shoulder season.

The new Skurka Series by Sierra Designs aims to fill this needed niche.

The first two items in the series are the High Route 1FL tent and the Flex Capacitor pack.

I had the opportunity to give both of these items a test run this past weekend.

In this article, I’ll be looking over the Flex Capacitor. 

Initial impressions?

Right of the bat, I was reminded of two packs: The popular ULA Circuit and the Osprey Atmos 65 pack. Not so much in features or appearance but in size, price and similar niche these packs will fill.

At 2 lbs 10 oz, the Flex Capacitor falls somewhere between the more minimalist-minded 2 lbs – 2 lbs 5 oz  $235 Circuit (depends on what is stripped out)   and the feature rich and hauling capabilities of the $259 Atmos at 4lbs 6 oz (!) .

At $199 retail, the Flex Capacitor is the least expensive of these three different options.

The Flex Capacitor has more padding and support than the Circuit, but not as much as the Atmos.  Depending on your use, a good balance.


A neat feature of the Flex Capacitor is the how it expands its storage capacity.

Every pack I’ve owned from an Eastern Mountain Sports 5500 back in the day to my current heavy hauler or solo packs uses an extension color to expand pack volume.

The Flex Capacitor? Some straps let it widen out for more capacity or cinch up when the capacity is not needed for something like a quick over-nighter.  No awkward high and tall profile that can throw off the center of gravity.  Not as critical on trail, but off-trail is when this high and off-center balance of a pack is very noticeable. As a shorter person with a broader stature, the pack fits me rather well. 🙂


Short, barrel-chested, thick eyebrows, hairy, can grow a heck of a beard, walks in the mountains a lot. Except Gimli has a full head of hair, too.

The pack closure is a zippered compartment with a top pocket on the brain of the pack. The top pocket is ample sized with good storage. I am not partial to a zipper closure and prefer a a cinch and buckle type closure. But that is my preference. I feel a zipper closure is more prone to failure in the field especially with longer term use.

The water bottle pockets are adequately sized if not overly generous.  The hip belt pockets are generously sized with a good amount of room for snacks or similar items.  There is a small mesh pocket on the front strap. For me, this mesh pocket is in the fish on a bicycle category. Others may feel different especially if wearing running shorts that have no pockets.  A quick and easy way to remove this pack strap pocket I did not plan on using would have been useful. As an aside, the Flex Capacitor has an internal bladder pocket that CAN be removed.

Due to the strap system, there is no front “shove it” pocket.   Not a criticism, but an observation that may or may not matter to the individual. The unique pack cinching capacity straps is the reason for this lack of a front “shove it” pocket obviously.

How does it wear?


Off-trail in the Buffalo Peaks Wilderness. Riding low and wide. Also, notice the small mesh pocket on the strap.  Alas, I could not find a better model for this pack… 😉

For my initial test run, I loaded up some shoulder season gear. The High Route 1FL tent, a thicker puffy, thicker pad and similar type of gear.  The load was not minimalist.  In other words, more typical of the equipment load expected when using a pack of this type.

With little futzing, I was able to get the medium sized pack fitting rather well.

It was very comfortable on single track , off-trail and also with some moderate bushwhacking. I was not worried about this pack tearing as with more minimalist packs nor snagging as with packs that have a higher profile.

After the initial fitting, I did not need to adjust the pack once over the weekend.

The buckle and strap system for adjusting the pack is simple and effective.

Overall impressions?

Overall, I think this pack will work well for the  person who needs a quiver of one for prime three-season use and even into deep shoulder season. At $199 it is a reasonably priced pack and does not weigh that much especially when compared to something such as the Atmos .

More minimalist solo backpackers can probably get away with the sturdy, but still pretty light, ULA CDT for a variety of needs.

But if your base weight is a little higher, need a more versatile pack with better weight hauling capability, prefer more support/comfort and need more storage capacity, a different pack is preferable.

The Sierra Designs Flex Capacitor could easily fit this set of requirements.  The ULA Circuit is a bit lighter but does offer not quite as much support concerning padding or suspension. The “S” straps of the Circuit fit many women well, however. Ultimately pack choices comes down to fit and comfort for the user as to which pack works better among similar types of packs.

With its competitive pricing, reasonable weight, low profile, unique storage capacity method and paired with a good suspension,  the Sierra Designs Flex Capacitor is potentially a worthy option for a Jack of All Trades gear kit.

The Sierra Designs Flex Capacitor is a pack for those who don’t need, want or can’t have a whole quiver of packs… but does need at least a damn good one.


Disclosure: The Sierra Designs Flex Capacitor pack was loaned to me by Andrew Skurka. 

Notify of

Inline Feedbacks
View all comments
Ryan Verma
Ryan Verma
7 years ago

Hi, thanks for your opinions on the flex capacitor. I’m looking for a new pack that will primarily be used for traveling (backpack style international travel) but it may also serve double duty as a camping backpack (I’m currently using the exos 58 and am very happy with it) .
Do you have an opinions on the comfort while carrying loads of up to or around 50lbs with the flex capacitor versus the atmos 65 or any other packs you can think of that might fit my needs?

Nolan Colucci
Nolan Colucci
7 years ago

I must be lost but don’t the compression straps change the volume of a pack already?

I dont see the advantage of having two compression strap systems.

7 years ago

I have a GoLIte Quest 70L that has a 1000 miles on it or so and this pack seems like a cousin to or even natural evolution of the Quest (@3.1lbs w/ frame sheet).I take it heavy winter hauling and for quick summer overnighters. Thanks for the review. I’ll definitely be checking out the Flex if my Quest needs to be re-homed.

7 years ago

I’m going for a 10 day hike on the Appalachian Trail starting at harpers ferry and then ending further south. We will hit a town to restock half way at about 5 days. You think this pack would be enough to carry 5 days of food, sleeping bag/blow up mat, 2 sets of clothes, and down clothes for night, light jacket and rain gear all comfortably? It’s looking like my brother and I will be sharing a tent and dividing the load at about 40-45lbs each and that will decrease as we eat approximately 2lbs per day.

James Johnston
James Johnston
4 years ago

The pack strap pocket is practically tailor-made for a 0.7 liter SmartWater bottle. It’s one of my favorite features of the pack!