How to Choose Sleeping Bags for Backpacking
Big Agnes Sidewinder SL 20 Sleeping Bag - Men's
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If you're a side sleeper who tosses through the night, the men's Big Agnes Sidewinder SL 20 sleeping bag is ergonomically designed to move with you as you roll, keeping you cozy and comfortable.
Shop similar productsKey Details
Fill
650-fill-power DownTek/FireLine ECO
Temperature Rating (F)
20 degrees (F)
- Ergonomically contoured, technical fit patterned to move with you as you roll from one side to the other, while ensuring warmth and comfort as you settle into position
- 650-fill-power DownTekâ„¢ insulation offers lofty warmth throughout with a PFC-free water repellent finish to keep you dry, even if when wet
- Body-mapped FireLineâ„¢ ECO synthetic insulation alleviates pressure points at the hips and feet while retaining optimized warmth
- Made from post-consumer recycled polyester, FireLine ECO maintains high loft, compressibility and durability with excellent weight-to-warmth ratio
- Ripstop shell fabric and smooth, polyester taffeta lining are treated with a PFC-free water repellent finish to help keep you dry and warm
- Jacket-style hood keeps insulation close around you without sacrificing mobility
- Stretchy mesh Pillow Barn built into the hood keeps your pillow in place; interior access from either side allows for easy adjustments
- Specially designed footbox mimics the shape and position of your feet while lying on your side for an optimized fit and thermal efficiency
- Smooth, antisnag locking zipper and zipper garage ensures no drafty cold spots
- Low-profile cordlock hood and insulated draft tube allow easy one-handed operation to seal out cold drafts
- Exterior loops allow you to easily hang dry or store bag when not in use
- Compatible with virtually every type and size of sleeping pad (not included)
- Includes storage sack and stuff sack for compact packing
Imported.
View all Big Agnes Backpacking Sleeping Bags| Best Use | Backpacking |
|---|---|
| Temperature Rating (F) | 20 degrees (F) |
| Temperature Rating (C) | -7 degrees (C) |
| Ultralight | Yes |
| Shell | Ripstop nylon |
| Zipper Location | Front |
| Insulation Type | Down / Synthetic Blend |
| Water-Resistant Down | Yes |
| Fill | 650-fill-power DownTek/FireLine ECO |
| Sleeping Capacity | 1-person |
| Lining | Polyester taffeta |
| Sleeping Bag Shape | Mummy |
| Stuff Sack Size | 8 x 17.5 inches |
| Stuff Sack Volume | 14.4 liters |
| Gender | Men's |
| Sustainability | Contains recycled materials Down certified to the Responsible Down Standard (RDS) |
Buying Advice
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Most Helpful Favorable Review
Very Comfortable 20 Bag
Xander4 years ago
I've had this bag for about 2 months now. I slept with it in 28 degree weather in Colorado while it was pouring rain outside my tent, and I was 100% warm. I slept on a yoga mat. If you plan on sleeping outside a tent while the weather is in the 20s, you'll want a liner, an additional trail quilt and/or a heavier sleeping bag.
I'm 6' tall. I bought the long.
The reason I bought this bag is because I valued compression size over weight. I have a 37 liter pack so I needed a bag that would save space. After sleeping out for 7+ nights, I can happily say that I made a smart decision with this purchase.
You can sleep on your back with this bag. I do it all the time in a hammock.
Xander
Colorado Springs, CO
24 people found this review helpful
Most Helpful Critical Review
Not an award winner
R1200GSA4 years ago
1st off this is a cold 20deg bag feels more like a 30deg in the field. But that us not it's worst offense. This thing leaks down like a sieve! If you sleep on your side you tend to move around a lot after a recent 4 day trip my tent floor looked like an Audubon murder scene each morning and it isn't leaking out of just the seams but the fabric itself. The zipper catches all the time and the shoulders are very narrow which makes rolling around even more difficult. I think that the variable padding design is good in concept but my hips were still complaining the next morning. I wanted this to work but it just doesn't. Makes me wonder if the folks who recently gave it an award actually slept in it...
R1200GSA
Albuquerque, NM
22 people found this review helpful
Customer Images
Xander
Colorado Springs, CO
Very Comfortable 20 Bag
4 years ago
I've had this bag for about 2 months now. I slept with it in 28 degree weather in Colorado while it was pouring rain outside my tent, and I was 100% warm. I slept on a yoga mat. If you plan on sleeping outside a tent while the weather is in the 20s, you'll want a liner, an additional trail quilt and/or a heavier sleeping bag. I'm 6' tall. I bought the long. The reason I bought this bag is because I valued compression size over weight. I have a 37 liter pack so I needed a bag that would save space. After sleeping out for 7+ nights, I can happily say that I made a smart decision with this purchase. You can sleep on your back with this bag. I do it all the time in a hammock.
Age:35–44
Weight:200–225 lbs.
Height:6'0"
Yes , I recommend this product
Beluga
Very comfortable but sheds a lot
1 year ago
I have a collection of sleeping bags at this point, and this is by far the most comfortable I've used. Having the zipper in the middle is really a game changer for side sleepers. Plus this bag is quite roomy, feels like you're under a blanket. The only negatives are that it sheds a lot, I mean A LOT. Everything was covered in feathers after a night in this, looked like a goose massacre took place. The other negative is that this bag is not very compact. I ended up buying a 15L compression sack, but even with that its still quite large. So something to consider if you plan on using this for backpacking. Personally though, that extra weight and space is worth the comfort this bag provides.
Age:18–24
Weight:200–225 lbs.
Height:6'1"
Yes , I recommend this product
R1200GSA
Albuquerque, NM
Not an award winner
4 years ago
1st off this is a cold 20deg bag feels more like a 30deg in the field. But that us not it's worst offense. This thing leaks down like a sieve! If you sleep on your side you tend to move around a lot after a recent 4 day trip my tent floor looked like an Audubon murder scene each morning and it isn't leaking out of just the seams but the fabric itself. The zipper catches all the time and the shoulders are very narrow which makes rolling around even more difficult. I think that the variable padding design is good in concept but my hips were still complaining the next morning. I wanted this to work but it just doesn't. Makes me wonder if the folks who recently gave it an award actually slept in it...
Age:45–54
Height:6'0"
No, I do not recommend this product
Jillian R
Sparks, NV
Beyond Expectations
3 years ago
Just used this bag this weekend near Sierraville CA. Im 5'8", 195lb. I went with the mens version as it was the only one in the store and I decided I wanted the extra room. This bag lets me stretch a lil more and was still warm enough. Granted the weather was warmer, but being roomier gives me more space to add layers. There was a good amount of feathers that came out after some tossin and turning in my sleep. However it's a factor I'm willing to deal with since I got to do my normal sleep and was not woken up due to restrictive movement like in my other sleeping bags.
Age:35–44
Weight:175–200 lbs.
Height:5'8"
Yes , I recommend this product
Jeanne
Seattle, WA
Best night’s sleep I’ve ever had camping
3 years ago
This sleeping bag is so comfortable and warm. I just spent four nights in a row sleeping in this bag, and it was the best camping sleep I’ve ever gotten! I am a side sleeper and mummy bags gave me hip pain, so I did quite a bit of research and settled on the sidewinder. This bag allows me to sleep with my knees and feet in a variety of positions. I am a 5’10 woman, but this bag fits me perfectly!
Age:35–44
Weight:150–175 lbs.
Height:5'10"
Yes , I recommend this product
Grumpy
West Virginia
Great for side sleepers.
1 year ago
This is my second one. The first one I used on my through hike of the Appalachian trail in 2022. It performed well in all temperatures. I used it the entire trip. On the coldest nights it kept me warm on the hottest nights I used it as a quilt. I destroyed it by not heeding the washing instructions and wash it with normal detergent. The down clumped together and I couldn’t get it to separate. The insulation was destroyed.
Age:65–74
Weight:150–175 lbs.
Height:6'1"
Brian M
North Texas
What side sleepers have been looking for
3 years ago
Best sleeping bag I’ve ever used. Great for a side sleeper such as myself. I’ve never been able to sleep on my back like a mummy except for a few minutes here and there. This is the bag you have been looking for, fellow side sleepers.
Age:45–54
Weight:175–200 lbs.
Height:5'8"
Yes , I recommend this product
Andrew G
Nice features for a 3 season bag
3 years ago
So far like this bag. Its not the lightest and not the warmest, but its certainly comfortable for side sleepers. One thing I have experienced with down bags is migration of the down during use. Although this happens a little with this bag, the denser nature of the fill seems to allow the down to stay in place and not leave too many empty areas. I put my head inside the bag after a nights sleep and there were very few spots where I could see daylight - i.e. issues with down distribution. The pillow pocket is nice and it works! The phone pocket also works for a normal sized phone, but might be too small if you have one of those oversized phones. The bag packs down OK too, especially if you put it in a dry bag and push all the air out before sealing it. Not the smallest, but not unacceptably bad that you can't put it easily in the bottom of a backpack. I recommend this bag for 30F and up. I would not push it below that, unless you want to wear a bunch of extra layers when in the bag, or you sleep exceptionally warm. Negatives. Well there is the zip, the zip and the zip. Like other reviewers, yes the zip snags, you have to be very careful operating this. Big Agnes, if you are reading this, please fix this problem, this should be a problem of the past. I also saw another comment that it leaks feathers through the fabric. Yes occasionally you do see a few feathers come through the fabric, but its not serious. When I got the bag, I air fluffed it in the tumble dryer and saw no feathers in the dryer filter and none in the bottom of the tent after use. I think this is a non issue.
Dean418
Taller? Get the extra long!
3 years ago
I'm 6'4" and usually a regular size bag works for me; and when I'm at home I'm a side sleeper so tried the regular size initially. The regular size ended up being too small for my side sleeping position because of how I pointed my toes and bent my knees so I exchanged it for the long size. Now it fits perfectly and is super comfy and warm! If you're on the fence about sizing up I'd definitely recommend it.
Age:25–34
Weight:200–225 lbs.
Height:6'4"
Yes , I recommend this product
Scoutmaster Tech
Fort Worth, TX
Warm, Roomy - Abysmal zipper/material interaction
2 years ago
Reviewer: cold-sleeper, side sleeper. Base layer pants, shirt, Merino wool socks Conditions: February, Dry night, 15-20mph gusting winds, 28deg., open air tarp shelter. Weight as used: 1128grams (2lbs 8oz. exactly as advertised) I was very pleasantly surprised at the warmth and fit of this bag. I've had several bags before that were "cut for side sleepers" and for this cut they were often too roomy and I was chilly in them. I feel that this bag got the fit just right and the insulation management dialed in for comfortable sleeping and heat retention. Looking through the bag in the morning sun I was able see a silhouette and uniform distribution of the insulating material. In my last 2 test bags I was able to easily see where the down was (dark spots) and WASN'T (lots of very light spots). In THIS bag, it was clearly a uniform distribution with lightly shaded insulation throughout each baffle and no major cold spots. The foot box was roomy as well and the FireLine material (never heard of it before) seemed to reduce those cold shocks you find as you kick around. The baffle along the zipper also worked well to keep out any drafts; I felt no leaks there. But that's where the baffle's useful ends. The zipper-and-baffle do NOT play well together! This is a snag-ful zipper, NOT snag-free. Overall the bag was comfortable and work, while all this is well and good, there is this HUGE caveat of snagging the zipper at nearly every opportunity. The baffle material is easily caught in the zipper from knee to nose at least 10-12 times getting in the bag and getting out. Other reviewers across the internet have said the same thing and I fully agree with them; this zipper or the baffle or both are TERRIBLE. Ultimately I believe it's a baffle fill issue: either too much material for the amount of fill, or not enough fill to keep the material out of the zipper path. The open/close issue would be enough to get rid of ANY other bag, but this bag is so dang warm and roomy - I'm not sure I'll be returning it. If Big Agnes reads these, you've got a good design with 2 small changes: (1) bump to 850FP (2) draft tube change - either more fill or less material. The problem is that the draft tube material gets caught in the zipper and needs to loft more to avoid bunching up and snagging. Final point: If you can deal with a snagging zipper (A LOT) because you're looking for a sub $300 bag with below average weight and above average warmth for a side sleeper - this is pretty dang good option. Just don't say I didn't warn you about the zipper.
Age:45–54
Weight:175–200 lbs.
Height:6'0"
Yes , I recommend this product
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