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  • Insulated with high-loft 650-fill-power duck down for warmth, light weight and compressibility; Ultra-Dry Down™ water-repellent treatment protects down from moisture
  • Ultra-Dry Down is a water-repellent polymer treatment applied to the 650-fill down; Ultra-Dry Down retains 60% more loft and absorbs 30% less moisture than untreated down
  • With a European Norm (EN) lower-limit rating of 32°F, it will help keep you warm in mild weather
  • Shell fabric is constructed of 2D PermaShell™ technology, a high-density weave, 33-denier fabric treated with a durable water repellent (DWR) finish
  • Shell material is highly vapor permeable and downproof
  • Lining is a breathable, durable 40-denier nylon fabric with a soft touch
  • Full-length side zipper and foot zipper allow bag to be converted from sleeping bag to a duvet/down comforter; this also allows 2 Sea to Summit bags to be zipped together
  • Oversize draft tube backing the 2-way zipper keeps the warmth in and the cold out; zipper is backed by stiff, antisnag tape for smooth operation
  • Semirectangular shape provides more room than a mummy bag for a more comfortable sleeping bag while maintaining thermal efficiency
  • 2-dimensional hood features drawcord adjustment to cinch and tighten around head; hood is designed to open flat when sleeping bag is used as a duvet/down comforter
  • Differentially cut inner layer is smaller than the outer layer to create a consistent thickness of insulation that precludes cold spots
  • Large zippered interior security pocket is great for stowing a few essentials, alleviating middle-of-the-night fumbling and preserving battery performance in cold weather
  • Baffle construction allows the down to remain fully lofted and keeps it from shifting
  • Sea to Summit Trek Tk II bag comes with a Ultra-Sil® compression sack


View all Sea to Summit Men's Sleeping Bags

REI membership


Best Use Backpacking
EN Lower Limit 32 degrees Fahrenheit
EN Comfort 41 degrees Fahrenheit
Temperature Rating (F) 32 degrees Fahrenheit
Temperature Rating (C) 0 degrees Celsius
Weight 1 lb. 13 oz. / 2 lbs. 2 oz.
Shell Nylon
Zipper Location Left
Insulation Type Down
Water-Resistant Down Yes
Fill 650-fill duck down
Fill Weight 12 / 14 ounces
Lining Polyester
Sleeping Bag Shape Semirectangular
Fits Up To (in.) 72 / 78 inches
Shoulder Girth (in.) 60 / 61 inches
Hip Girth (in.) 59 / 60 inches
Stuff Sack Size 7.5 x 14 inches
Stuff Sack Volume 10 liters
Compressed Volume 5.1 / 5.5 liters
Gender Men's
Rated 5 out of 5 by from Great Summer Sleeping Bag! Great bag, I was toasty warm on all my summer trips thus far (never got below 40degrees). The zipper on this bag really doesn't catch which is a problem I have on all my other bags. Also there is a separate zipper for your feet so you can vent just at the bottom. The bag is very roomy, which is surprising since it is so lightweight and packs down so small, it is bigger than the foot print of my thermarest!
Date published: 2012-09-06
Rated 5 out of 5 by from Perfect for folks afraid of mummies My first mummy bag, and I was really pleased with it on its first outing in 37 F weather. I'm a spread-eagle sleeper, and mummy bags are too confining to me. However, I needed a really small, lightweight bag for backpacking. I compared dozens of bags and picked this one because it appeared to be wider in the footwell, have a wider top so I can put my elbows out, and is quite light weight. The footwell is a perfect compromise between typical mummy bags and a rectangular bag. I had enough room to not feel cramped. The top has a wide opening, and lays flat--perfect for spread-eagle elbows--but it cinches up nice to make a warm halo. I know super-light-weight gear can tend to have wimpy zippers, but this one seems good to me. Had no snag troubles. Time will tell. Temperature performance was great in 37 F (thermals, an extra t-shirt, thick socks). We'll see how breathable it is during the summer hikes, but I'm expecting it to be fine. I think this was the highest-priced bag I considered, but the room, the light weight, and the 3 bags it comes with (cinch, stuff, washing) help the overall value.
Date published: 2013-05-03
Rated 5 out of 5 by from Perfect Light-Weight Summer Duty Bag The Trek I is a good choice for lightweight comfort in summer and mild weather. Sea to Summit obviously put a lot of thought into this bag: - Roomy rectangular shape is a bit retro, but roomy - Hood can be relaxed completely in warmer weather - Unzips completely into a comforter for warmer nights - Zipper design won't snag on the bag (really!) - Right- and left-side bags can be zippered together - Compresses down nicely to about 5L with included dry sack - Included storage bag won't roll off the top shelf in your closet Fair-weather campers, and travelers looking for a crash bag, will appreciate saving a bit on both weight and bulk (especially compared to synthetic bags). The Trek's not the lightest or smallest bag that money can buy, but it's also not $400. If you're a minimalist looking to squeeze every gram out of your gear, this may not be the ideal bag for you—but if your camping plans don't call for a bag that's comfort-rated down below about 40˚F, and you need an affordable, comfy, lightweight bag your really should consider taking a closer look.
Date published: 2012-02-13
Rated 5 out of 5 by from Perfect bag for kayak trekking Purchased this bag before my last week long kayak trip in Maine. Wanted a bag that was a bit smaller than my current down bag but still was warm. This bag compresses so small I fit it in an 8L dry bag. Showed one of my fellow paddlers my new bag before the trip and he purchased one as well. This bag was warm, love the rectangular shape foot as I tend to toss and turn a bit and mummy bags generally are a bit confining to me.
Date published: 2016-01-11
Rated 4 out of 5 by from It's fine It's got a zipper at the foot which i don't need. The zippers overlap, but occassionally I must bump it or fail to close it all the way, and it opens an inch, and I can feel my feet geting cold. It's a feature I don't need, but maybe desirable to others to keep feet ventilated and dry. Rated for 32 deg F. I would say that's accurate. Used it in 30 deg F weather with 65% humidity. I was warm, although i did sleep in about two layers plus toboggan and gloves, and nalgene bottle filled with hot water in ziplock bag. It'll pack down to less than football size, but I don't want to crush the feathers. I don't need the space so i only lightly compress it. Comes with fancy washing bag, and long term storage bag. Face hole cinches with a draw cord. Works well enough. Bag always fluffs out fully after I roll it out.. I like it. Perhaps wish I got a bag with a few more ounces of feathers, to hold the heat even better. I'm thin, and could use the extra insulation. But I like the lightweightness of this bag. Net weight is accurate. Am pleased with the bag.
Date published: 2013-12-08
Rated 4 out of 5 by from Great, Warm, Diverse Sleeping bag The Sea-to-Summit worked well in 35 degree windy weather. I was a little cool in the night from the ground, but considering I didn't bring a sleeping pad, the sleeping bag worked pretty well. The hood closed well to keep my head warm during the night as well during the windy nights. I wouldn't take this sleeping bag much below freezing temperatures, but it worked well for the situation I was in.
Date published: 2013-05-27
Rated 4 out of 5 by from You can't beat this bag...kinda.... Getting the bad out of the way: This bag is clammy, especially in the foot box. Using this bag in an open-air cabin with 30mph gusts of winds, I had to keep the top half of this bag unzipped. I feel this bag relies less on its down fill and more on the material to achieve its 32 degree rating. I would wake up hot and open up the bag. Then wake up cold and have to close it up. And the zipper does snag a little bit. Not as bad as other bags. Just get used to it. It will always happen no matter what bag you have. Onto the good: This bag packs down really small. It fits in the Sea To Summit XS compression sacks with enough room to fit lightweight PJs. Its fairly lightweight too. The hood is great except for one thing: No face muffler. The hood opens flat so you can put your pillow in it and pull up the draw cords to keep it in place throughout the night. And lets face it, you only use your hood in extreme weather right? The fully openable feature is essential. This allows for good ventilation. After fussing around with it, I found the sweet spot: Open the side bottom to about thigh high. Then open foot box (Opposite side from open zipper) about 4 inches. This kept me more comfortable than before but still not perfect. I use this for work and it keeps me warm enough and comfortable enough in the tent or cabin. Traveling with this bag would put it to its best use. Folds open so you can use it like a comforter and in this position it is extremely comfortable. I haven't put it to extreme tests so I'm not sure how it would handle tough spots but based on Sea To Summit's amazing performance in the past (I own the xTI and a few other products. They are amazing) I would bet on it to deliver the goods. Final word: Although this bag doesn't do it all perfectly, there's nothing out there that does it better for the size/weight/accoutrements/$$$$$$$. Add a muffler and a bit more breathability and 5 stars all the way. Thanks for another great product S2S!!
Date published: 2012-10-20
Rated 4 out of 5 by from Good bag overall Nice bag, but a little light on the temp rating. I've spent more than one chilly night below 40 degrees in this bag. I think if you have a liner 32 degrees is attainable. It's lightweight and packs small. It's a bit small through the shoulders, but a nice compromise in the footbox. Good bag overall.
Date published: 2012-04-08
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Is there a way to order the right zippered version of this bag through REI? 

Asked by: geoffrey2011
No, ​REI does not place special orders. We recommend that you contact the manufacturer directly.
Answered by: REIservice
Date published: 2016-08-24

Hi there. Sea to Summit have resently updated this line. Is this the sleeping bag pictured or the newer version trek ii that has a orange exterior?

Asked by: Shannon
This is the 2016 version of the Sea to Summit Trek Tk I. It is not the newer model of the Trek I.
Answered by: REIservice
Date published: 2017-05-18

Just received my new sleeping bag and noticed that only 2 bags (storage cube and compression stuff sack) came with it. Some of the reviews state that there are 3 bags that come with it (cinch, stuff & wash bag). Please advise if I'm short a wash bag.

Asked by: Sashabarks
Sea to Summit only includes the compression sack and the black mesh storage bag with the Trek TkI Sleeping Bag.
Answered by: REIservice
Date published: 2016-08-09
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