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The Flex Capacitor features a unique patent pending gusset system that allows the pack to quickly and easily expand from 40-60 liters with the adjustment of a few straps. Instead of expanding up like other packs, the circumference of flex expands to provide a more stable and comfortable load carry.
Packbag Key Features
Suspension Key Features
|TORSO SIZE||16" - 19"||18" - 21"|
|VOLUME (Liters)||39 - 56L||42 - 60L|
|VOLUME (Cubic Inches)||2400 - 3400||2550 - 3650|
|WEIGHT||2 lbs. 9.2 oz. (With S/M hip belt)||2 lbs. 11.2 oz. (With M/L hip belt)|
|DIMENSIONS (LxWxD)||28.5" x 13 "x 10"||30" x 13" x 10"|
|MAX COMFORT WEIGHT||35-50 lbs.||35-50 lbs.|
|HIP BELT SPECS||XS/SM||SM/MD||MD/LG||LG/XL|
|HIP BELT FIT RANGE* (Inches)||<29||29 - 32||32 - 35||>35|
|HIP BELT FIT RANGE* (Centimeters)||74||74 - 81||81 - 89||89|
*This is a hip measurement, not a waist measurement. Please watch pack fit video to learn how to properly measure.
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Just got done with a six day packrafting trip in the desert and it was the ideal pack for the job. I went between 25 lbs (without packraft and water) to 45 lbs (packraft and 10 liters of water) making the compression system invaluable. I was shocked at how comfortable the pack remained at both weights, with great padding and a really robust frame compared to every other ultralight system I have tried. Oversize hip belt pockets and the incredibly convenient shoulder water bottle holder were amazing, and I even really liked the small brain compartment that prevented me from stuffing it with too many random things. I had to scrape through a couple of slot canyons on the trip and was impressed by the durability of the of the material as well. At $180 cheaper and only 4 ounces heavier then a frameless, pocketless, non size flexible Hyperlite, the Flex Capacitor is the way to go.
Oh and just a P.S. I got the wrong sized hip belt and the return process was fast, friendly, and painless. I am really impressed with the attitude and innovation of Sierra Designs. Nathan Savig on Mar 21st 2018
I took this pack on a 6-day, 5-night rim-to-rim backpacking trip in the Grand Canyon in 2017 along with several other multi-day trips in Colorado. I love MOST everything about it.
However, here are a few suggestions that I feel would improve the pack:
1) The lumbar pad needs to have a vertical recess in the middle to provide the spine vertebrae some pressure relief. On a long hike, the lumbar support made my vertebrae ache and I was constantly trying to adjust it to provide my back some relief (38 lbs);
2) This pack has a well located small top-cap zippered compartment. This pocket expands downward into the main compartment. The problem with this design is that the top compartment competes with the main compartment for space when the pack is fully loaded for a long outing. When the main compartment pack is full it can be difficult to close the zipper that joins the upper smaller compartment with the large main compartment. The suggested solution would be to have the top compartment have side walls that expand upward (as opposed to downward with the current design) which would allow for more usable room to accommodate those items that you want ready access too. As much as possible you really want to be able to pack each compartment independently from the other. They should not compete for the same space.
3) I'm 5'11' and 170 lbs with a 33-inch waist. The pack's main waist belt had to be re-tightened often. The curvature of my waist was just enough that the two cinches, one on each side of the main buck allowed the belt webbing to slowly slip through the plastic cinches. I found myself constantly retightening the waist belt. There either needs to be a true lock-down mechanism that pinches the waistbelt in such a manner that prevents it from loosening or there needs to be a better cinch selected that will not allow the nylon webbing to slowly release through each cinch as you hike along the path.
Small things but they were annoying enough to comment on. The Flex Capacitor is truly a wonderful, lightweight, backpack. I am scheduled to return to the Grand Canyon in May and I will be using this pack again but with a few modifications and knowledge of packing limitations between the main compartment and the smaller top compartment. Dean Stevinson on Mar 19th 2018
The Flex Capacitor is a great backpack. It’s light weight and comfortable. The hip belt sizing cart is spot on, trust it. If you’re using modern gear this pack will be great for you. If you have an old Coleman bag or take the kitchen sink with you this bag may not be for you.
I have never found a backpack I really liked until this one. The backpacks I’ve tried are: Lowe Alpine Centro 45+10 (hip belt was too big), SD Revival 65 (great frame, really bad sectioned hip belt), BD Mercury 65 (Really didn’t like the pivot), REI Flash 65 (I don’t even like talking about it). Needless to say, I’m picky. I’m skinny, so I have problems with hip belts fitting. I have a 29-inch waist and even when hip belt says it goes to 28 inches usually I’m completely maxed out on the tension. I ordered a S/M pack with an XS/SM hip belt because I had been burnt so many times in the past from other manufacturers. SD sizing is true, and I should have gone with the correct size according to the chart. Even with this mistake the pack did great. I had a total pack weight of 25 pounds. I didn’t get the usually hot spots on my hipbones. I like that the pack has the things I want and none of the stuff I don’t. It’s simple, but has stretch side pockets, hip belt pockets, and the shoulder pocket. The shoulder pocket is nice for a half liter of water and moves some weight to the front. It doesn’t have bottom or side access, or a sleeping bag compartment. I don’t like those features and I’m glad they are missing. I have a 17-inch torso and the pack fits fine. It doesn’t need to be adjustable. I was also happy to be able to remove the reservoir sleeve. My concerns about the back is that it is a small 60. It’s a zip top so there is no over loading the thing. The top pocket is small, so you must be selective on what goes in it. I’m going to change the zipper pull on the top pocket to a different color to limit confusion, between it and the main compartment. It’s a steal at twice the price. It’s worth a try.
Russ on Dec 1st 2017
I have not been a fan of top loading packs and purchased this pack because of its weight and my experience with other Sierra Design products. I took this pack out for its first trip on the Timberline Trail in late October. We had early snow at some of the lower levels and I was happy to have a lighter pack than I usually carry and pleased with my contents staying dry. I also found the pack to more comfortable than I expected. The only drawback I had with it, was lack of attachment strapping or hoops. Something can be remedied by adding later. Did use the compression straps on the front to hold my foam sleeping pad vertically, and that worked well. If the pack would have been maxed out, that's not an option. Very happy with this pack and will be my main pack from now on. Brian on Nov 18th 2017
I used the pack, for the first time, on a eight day cross-country backpacking trip in the Sierra. I have nothing praise for the overall design. My one dislike is the insufficient material at the bottom of the pack. The granite cut numerous holes in the material. I don't think the cloth is strong enough for cross-country hiking. I understand there is a trade off between weight and durability, but the lower section of the pack is durable enough. Steve on Sep 18th 2017
I took this pack out about a month ago for a three day, forty-ish mile trip in Desolation Wilderness. Before I bought this pack, I would have used my Gregory Z55, but I wanted to try something lighter, and so I ended up with this. I have no regrets. I really like having one big internal compartment rather than several-- makes it easier to stay organized (I always forgot which compartment contained what), and it allows you to weatherproof your load from inside the pack (as the guy recommends in the video). The external pockets were all the right size and easy to access, the load carry was super stable, and back ventilation left nothing to be desired. I really like this pack, and I plan to use it for longer trips. Unknown on Sep 8th 2017
I just returned from a 13 days trekking on what's called Europe's most difficult long distance trail. I've been so happy with this pack in the mountains. I did not fill it complete, so average weight carried was up to 12kg in the morning with 2L waterbladder filled. What is surprising is that with that load I do not feel the weight on my hips or shoulders. Thanks to the lumbar pad doing a lot of the carrying work ! but it is also not felt. My experience is that the load is spread over 3 zones instead of 2 as other packs do . (I was in Spanish Pyrenees last year with a high quality Lowe Alpine backpack and my hips hurt like hell and felt numb for weeks after the trip.) One of the 2 red straps at the bottom i used for holding the bottom of the trekking poles. Other people's remarks about missing straps to attach stuff was not an issue to me : I used the "expansion" straps for that and for sock and clothes drying :)
Steven(Belgium) on Aug 15th 2017
Just bought one of these great packs to start backpacking again. It has been 33 years since I last backpacked, too busy with many other outdoor activities (day hiking, trail running, mountain biking, backcountry skiing, snowshoeing, kayaking) and work has kept me from backpacking adventures. We just had out first trip and I could not be more pleased with this pack. Carried very well, super easy to pack and organize and was the perfect size. Thanks to SD, I am again super excited about backpacking again. I am now excited to buy one of the SD backcountry quilts for a sleep system. Woody Keen on Aug 12th 2017
I have used the pack several times, on backpacks and day hikes. It is my intention to use the pack for the John Muir Trail this summer and want to make sure it will work well. I have used the REI Flash pack for the JMT and that was not a good pack at all.
First off the positives. Well constructed, light weight, and carrys weight well. Large hip pockets are a big plus with good, snug side pockets for bottles, poles, chair, or whatever. You can access the side pockets while wearing the pack. Love the shoulder pocket and I use it to hold my iPhone for quick access. Hip belt stays snug (unlike the REI Flash BTW).
Now the negatives. I have a SD lightning 2 tent which has built in stays on each end that are about 14 inches give or take. This means I cannot carry the Sierra Designs tent effectively in the Sierra Designs Bag. It cannot be placed horizontally. I need it to be horizontal to be able to fit my bear can. So this is presenting a problem, especially since (my second issue), there is no bottom straps to carry a pad or the tent. I REALLY could use the straps on the bottom for a rolled up pad or a tent. I now have to find someone to add the straps. Third, it a very little thing, but the chest strap has no built in whistle like every other pack. Brian Decker on Jun 14th 2017
Literally the most comfortable pack I have owned. I am long and skinny and this pack with the ability to change out the hipbelt has been amazing. I have taken it on day hikes and overnights in the CO mountains lugging a ton of camera gear and it has fit wonderfully. The large pockets on the hipbelt are great and the other features are simple yet highly useful. My one negative that I like on other packs that I have is a dedicate insertion point (sleeve) for my ice axe. I currently slip it between the seam when in 40L mode and just am concerned I will pierce the pack at some point, but overall happy as can be! One pack to rule them all!!!!! Jason on May 18th 2017