How to Choose Sleeping Bags for Backpacking
Sea to Summit Trek TkII 18 Sleeping Bag
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With a tapered rectangular shape that offers more room than a mummy bag, the Sea to Summit Trek TkII sleeping bag keeps you warm via water-resistant, RDS-certified 650-fill-power down.
Shop similar productsKey Details
Fill
650-fill-power Ultra-Dry down
Temperature Rating (F)
18 degrees (F)
- Water-repellent, 650-fill-power Ultra-Dry Downâ„¢ retains 60% more loft and absorbs 30% less moisture than untreated down; down is also PFC-free and RDS-certified
- Responsible Down Standard (RDS) ensures the down does not come from animals that have been subject to any unnecessary harm, such as force-feeding or live-plucking
- Tapered rectangular shape offers more space than a traditional mummy bag while maintaining thermal efficiency
- Nylon shell fabric is treated with a durable water repellent (DWR) finish that sheds moisture and helps block wind
- Vertical chest baffles prevent down migration and 3D sidewall baffle maximizes loft right to the edge of the bag to prevent cold spots
- 2-way #5 YKK® side and foot zippers let you ventilate as needed; oversized zip draft tube keeps out the drafts, while antisnag materials make for smooth zipping
- 3D hood draws in tight to keep you cozy; neck collar draft tube seals in warmth
- 20-denier lining fabric is lightweight and soft on your skin
- Internal security pocket keeps nighttime essentials close at hand
- Comes with an Ultra-Silâ„¢ compression sack and a nylon storage sack
- This bag is designed to zip together with another to create a double bag
Imported.
Temperature ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth, since many different factors contribute to your comfort while you sleep. Backpacking bags are typically rated for temperature according to an independent testing protocol—currently International Organization for Standardization (ISO) 23537, though some older items followed European Norm (EN) 13537. Testing is based on a person wearing one base layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38.
Each bag then gets 2 ratings: the Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Some brands determine their own temperature rating by aligning to the Comfort rating for women’s bags, to the Lower Limit rating for men’s bags, or somewhere in the middle for nongendered bags.
View all Sea to Summit Backpacking Sleeping BagsEach bag then gets 2 ratings: the Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Some brands determine their own temperature rating by aligning to the Comfort rating for women’s bags, to the Lower Limit rating for men’s bags, or somewhere in the middle for nongendered bags.
| Best Use | Backpacking |
|---|---|
| Tested Lower Limit | 18 degrees (F) - EN |
| Tested Comfort | 30 degrees (F) - EN |
| Temperature Rating (F) | 18 degrees (F) |
| Temperature Rating (C) | -7.8 degrees (C) |
| Shell | 30-denier nylon |
| Zipper Location | Left |
| Insulation Type | Down |
| Water-Resistant Down | Yes |
| Fill | 650-fill-power Ultra-Dry down |
| Lining | 20-denier nylon |
| Sleeping Bag Shape | Semirectangular |
| Stuff Sack Size | Unavailable |
| Gender | Unisex |
| Sustainability | Down certified to the Responsible Down Standard (RDS) |
Buying Advice
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Most Helpful Favorable Review
Comfy and warm
caldwe5 years ago
I debated between this and the women’s version. Happy I went with the Trek just for the extra space to roll onto my side without getting tangled up and twisted in a conventional mummy bag.
I wish it had an internal comfort collar. Something my last bag had, but I see why not for weight reasons. I think I’ll learn to live without it though.
It’s so warm and comfy. I slept peacefully through a few cooler and rainy nights in Wells Grey park and woke up happy and dry. The last night warmed up quite a bit and I found myself quite hot and clammy. I’m glad I was able to unzip the foot box and dump some heat. I was still quite clammy and the interior liner was sort of sticking to me which was a bit annoying. Something that could be solved with a silk liner though. And being a down bag, I will probably get one anyway for lower maintenance in the future.
It’s pretty quiet. It’s not the loudest bag I’ve ever had, but you still get some of the swish swish if you move around in the night. I’m not a crazy light sleeper so it didn’t really bother me.
It came with a compression stuff sack which is a novel concept to me. Had to buy one for my old mountain hardware bag.
It’s SUPER lightweight and compresses quite small. For that warmth rating I was expecting no less than 3lbs so I was pumped to get it all in a 2lb package. I always love to save the weight and space in my pack.
I’m stoked about Sea to Summit after buying an entire lightweight sleep system this year. I don’t usually sleep too well camping, it this was a game changer.
caldwe
Kelowna, BC
10 people found this review helpful
Most Helpful Critical Review
Sticks to you like glue if you sweat
Helen3 years ago
The sleeping bag is very well made and high quality. But if you sweat even a little bit, the lining of the sleeping bag will stick to you like glue. I woke up in the middle of the night terrified that I had been tied up, and it took me a couple minutes to unwrap the sleeping bag from around my legs because it was sticking to me so tightly. I ended up returning the bag. I would not buy it unless you are going to be using it to sleep in 30 F degree weather. I was sleeping in about 50 F degree weather.
Helen
5 people found this review helpful
Velder
Oklahoma
Light, well made, I am 6'2" and fit well in long
4 years ago
Took this bag out and it got down to @ 24 degrees. I wore a base layer, flannel shirt, sweater, jeans, and some wool socks. If I took it any colder I would want a liner or sweatpants or something. I am 6'2" and have room to stretch out and not hit the end of the bag on the long version. Downside is my tent wasn't quite wide enough, so my feet were touching the wall. This resulted in the footbox being a tad damp, and my feet got chilly. Other than that, I cinched it up around my face and got a solid 8 hrs of sleep. Zipper takes some finesse in the dark. Packs down small and doesent weigh much. Happy with the product overall.
Weight:175–200 lbs.
Height:6'2"
Yes , I recommend this product
caldwe
Kelowna, BC
Comfy and warm
5 years ago
I debated between this and the women’s version. Happy I went with the Trek just for the extra space to roll onto my side without getting tangled up and twisted in a conventional mummy bag. I wish it had an internal comfort collar. Something my last bag had, but I see why not for weight reasons. I think I’ll learn to live without it though. It’s so warm and comfy. I slept peacefully through a few cooler and rainy nights in Wells Grey park and woke up happy and dry. The last night warmed up quite a bit and I found myself quite hot and clammy. I’m glad I was able to unzip the foot box and dump some heat. I was still quite clammy and the interior liner was sort of sticking to me which was a bit annoying. Something that could be solved with a silk liner though. And being a down bag, I will probably get one anyway for lower maintenance in the future. It’s pretty quiet. It’s not the loudest bag I’ve ever had, but you still get some of the swish swish if you move around in the night. I’m not a crazy light sleeper so it didn’t really bother me. It came with a compression stuff sack which is a novel concept to me. Had to buy one for my old mountain hardware bag. It’s SUPER lightweight and compresses quite small. For that warmth rating I was expecting no less than 3lbs so I was pumped to get it all in a 2lb package. I always love to save the weight and space in my pack. I’m stoked about Sea to Summit after buying an entire lightweight sleep system this year. I don’t usually sleep too well camping, it this was a game changer.
Yes , I recommend this product
Helen
Sticks to you like glue if you sweat
3 years ago
The sleeping bag is very well made and high quality. But if you sweat even a little bit, the lining of the sleeping bag will stick to you like glue. I woke up in the middle of the night terrified that I had been tied up, and it took me a couple minutes to unwrap the sleeping bag from around my legs because it was sticking to me so tightly. I ended up returning the bag. I would not buy it unless you are going to be using it to sleep in 30 F degree weather. I was sleeping in about 50 F degree weather.
Height:5'10"
Age:25–34
Weight:150–175 lbs.
Susan B.
Solid bag comfy
4 years ago
Really like this bag. Plenty of room and lightweight. Purchased the 18 degree bag and tested it in Alaska for a week of both dry cabins and tents. Temperatures varied from high 30s to mid 50s. I am cold natured and was a bit cool in the tent in the 30s despite wearing wool layers, but again I am always cold. The bag is comfortable and seems well made. I like having both the regular storage and compression sack for backpacking. My biggest complaint is that it is really smelly. I have not had down bags smell quite this much. Any suggestions on ways to de-funkify it would be appreciated!
Originally posted on Sea to Summit
Where L.
Thoughtful construction for warmth and comfort
7 years ago
I bought this bag and immediately spent 17 nights in it. The lows were in the twenties most nights. The Trek 1 provided warmth and comfort. The cut of the bag is comfortable and great for someone that may like to alternate sleeping positions during the night. The baffles around the zipper and foot box held all drafts out. (sleeping under tarp). The cinches down tight. The bag packs down tight and dries out quick when wet. I train wilderness instructors and everyone that saw it and inspected it was impressed by the level of construction and details put into the bag.
Originally posted on Sea to Summit
Kilgore Trout
Olympia Wa
Great bag with an excellent roomy footbox
4 years ago
I bought this bag for my wife and now I'm thinking about getting one for myself. It's very warm ,reasonably light and has the best sleeping bag footbox I've ever used. The footbox has its own zipper for venting and when fully unzipped, along with the main zipper, allows the bag to lay flat like a blanket. Im sure this feature adds a little weight but it's very much worth it to me as someone who tends to get hot when sleeping.
Height:6'3"
Yes , I recommend this product
Happy C.
Where to start?! Warm, ability to open foot area to reduce heat on hotter nights and ability to use as a blanket
7 years ago
Where to start?! This sleeping bag has so many great features. I have been looking for a sleeping bag that has a low degree temperature rating and could be coupled with another to make a double wide sleeping bag for two. I found all I wanted in the Trek plus a lot more. The low temperature rating has kept me warm and cozy during cold fall nights and mornings. It also has kept me the perfect temperature during summer nights by unzipping it all the way and using it as a blanket. The outside and dry down feathers have stood up to condensation and when a leak magically appeared in the top of my tent. My partner and I have also enjoyed the ability of zipping two Trek sleeping bags together to for one large sleeping bag we can sleep snugly together in. Great bag!
Originally posted on Sea to Summit
Michael S.
Not quite sure this is
5 years ago
Not quite sure this is the right bag for me. Quality seems really good zippers and all. But when trying to sleep in it for a week of cool summer nights in our camper (50-60 degrees) in my boxers, and tee shirt, it was not comfortable to me. I was warm enough, but it felt like saran wrap type sticky-ness on my legs as the bag wanted to cling to me. I was clean and not sweating but it felt too weird to me. After one night I just opened it up used it as a top blanket comforter, and put a blanket under me. I do not sleep in pajamas so I guess I will have to buy a thin liner for it? hmmm. I bought it for backpacking due to the weight/quality and fall weather temps, so looks like I need to make an adjustment to my use. none of my synthetic bags I have feel like this too me when I sleep in them.
Originally posted on Sea to Summit
Ken
Lightweight and Cozy
6 years ago
Light as a feather and warm enough to keep me comfortable throughout the night, I was surprised just how well the sleeping bag performed in the Adirondack Mountains. I used S2S's sleeping mat to go along with it, and I have NO complaints! It actually was warm enough to make me open the bag a little bit for a little cooling! It was easy to pack with the accompanying compression dry sack and made my camping experience pleasurable.
Originally posted on Sea to Summit
Teal G.
Sweet bag holds up to SE Alaska Summer
4 years ago
Took this bag out on a sea kayaking trip in Juneau. It poured and everything was damp. Not only was I dry and toasty, but the foot zipper was clutch when the tent got too warm. This bag is made well, fabric is nice and comfortable. Dried quickly when exposed to swamped kayak conditions. Would buy again and recommend for anyone looking for a solid versatile bag. Also shipping was fast and customer service off the hook!
Originally posted on Sea to Summit
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