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REI Kilo Flash +40

The Kilo Flash +40 has been discontinued. If you're looking for something new, check out the best warm weather down sleeping bags for 2021.

photo: REI Kilo Flash +40 warm weather down sleeping bag


Price Historic Range: $69.83-$79.83
Reviewers Paid: $90.00-$189.00


2 reviews
5-star:   1
4-star:   1
3-star:   0
2-star:   0
1-star:   0

I have owned my Kilo Flash 40ºF sleeping bag for about 6 months now, and I have spent enough nights in it to confidently say it is true to its temperature rating. I consider this factor the single most important consideration for a sleeping bag, because if a bag cannot keep me warm to a temperature reasonably close to its rating, it is useless to me. I realize that every time I venture out in the backcountry, any amount of uncontrollable factors could collude to put me in a dangerous situation; if my sleeping bag cannot be counted on during these times, I have no need for it.

From the moment I inspected the bag I knew it was put together well, and, indeed, after the 20+ nights I have spent in it I’ve lost only about 10 feathers. The seams are solid, and reinforcements show up exactly where one would expect them (both ends of the zipper, top of the draft tube). Both the shell and lining are of very high quality as well: the DWR coating does a nice job of keeping tent condensation and blowing mist at bay, and the drape provided by the supple lining allows the 750-fill power down to loft unimpeded. Speaking of loft, this bag plumps up quite nicely; each baffle is well-stuffed, with no one baffle standing out from the rest as being under-filled. Top layer loft is approximately 2” for those who like to know these things.

I am 6’-1” tall, 160lbs, and the long version fits me perfectly. By “perfectly,” I mean this bag strikes an ideal balance of thermal efficiency and wiggle room. While I would label myself as either a “warm” or “cold” sleeper, I often find myself sleeping on my side or stomach, and the Flash’s torso is roomy enough to allow my tossing and turning without the bag moving with me. I can get a knee out to the side in the leg area, and the footbox is roomy enough to stash a Nalgene and a spare set of clothes. On the odd chance the bag does roll with me, a 60/40 top-to-bottom distribution of down keeps my backside from getting chilled. I’ve used the Kilo Flash in temperatures ranging from the mid-sixties down to 28ºF, in both a single wall tent and under the stars, and it has performed admirably well in every respect.

At temperatures below 40ºF, the necessary addition of layers is accommodated nicely by the sleeping bag; at the low mark of 28ºF, however, the clothing required to stay comfortably warm did restrict my movement considerably. Wearing Patagonia Capilene 3 base layers under a Patagonia R4 fleece and polypro bottoms, with two pair of mid-weight wool trekking socks and a fleece beanie, kept me toasty-warm the entire night through, although I really couldn’t do much besides move my arms from the hands-clasped-across-my stomach position to the arms-lying-at-my-sides position, and cross my legs. For reference, all testing was done on a full length 3/8” closed-cell foam pad, and I expect that with the addition of a second, torso-length inflatable pad, this sleeping bag could be pushed into the lower 20’s by those with a good amount of determination.

Of course, this level of warmth would not have been possible without the impeccable design of the Kilo Flash’s minimalist—but effective—features. The draft tube covers the stiffened zipper completely, while the face muff creates a very tight seal when fully cinched down. Differentiated drawcords provide a fast, fumble-free way to adjust the hood at night should temperatures change drastically, and the amount of down used in the hood is not skimpy by any measure. Pad loops are there for those who wish to use them, but I have cut mine off to save a bit of weight as I’ve never liked the confined feeling of an attached sleeping bag/pad combo. REI has also included a single, hook-and-loop-secured inner pocket large enough to store a watch and headlamp within easy reach.

The Kilo Flash packs down to a cylinder 6” in diameter and 6” long by means of the included sil-nylon compression sack, and it all but disappears into my pack. At 1lb-6oz—again, for the long version—it is incredibly light, too. The single logo is heat-transferred, and the ¾ length zipper reduces weight further while still allowing a more open, quilt-style sleeping configuration in warmer weather. The light weight and laughably small packed size of this sleeping bag has allowed me to completely reorganize how I load my pack, providing me many more options as far as distributing pack weight goes. I find myself leaving my Marmot Helium bag in the closet more often now that I have this beauty, which is quite a testament to the warmth and versatility of the Kilo Flash.

Design: Slim-fitting mummy
Fill: 750 fill down
Temperature Rating: 40ºF
Weight: 1lb 6oz
Price Paid: $90

'Pros' for this bag are: compression and weight. Warmth is good - I was comfortable sleeping nights in temps down to the 40s inside a tent.

The only 'Con' I can come up with for this bag is the size. I'm 5' 10" 175 lbs. Using the regular size bag (there is also a 'tall' model available), I was feeling a bit cramped. I fit in the bag length-wise, but just barely. Girth was very tight.

I spent a week in the Wind Rivers in Wyoming in late August. We had a mix of warm and chilly nights. On the coldest night (probably down to about 40 deg) I had to put on some extra clothes. Then I was fine. On warmer nights, I was not overheating. When it came time to pack up and go, this bag packs down to a ridiculously small and light size. Absolutely tiny. Miniscule. I'd highly recommend this bag for summer trips unless you're a really cold sleeper; or a larger dude.

Design: tight mummy
Fill: 750 fill down
Temperature Rating: 40 f
Weight: 1 lb 3 oz
Price Paid: $189

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