Campman Outdoor Gear & Apparel

Your sleeping bag might be the most important part of your camping kit. If you forget your tent at home, you sleep in the open air. If your sleeping pad deflates at camp, you might be uncomfortable, but you’ll make it through the night.

But without your sleeping bag, you’re probably driving back home and calling it quits on your camping trip altogether.

And since it’s your most important piece of gear for sleeping under the stars, it’s also vital that your bag conforms to your personal sleep style, not the other way around.

The Big Agnes Sidewinder Down Sleeping Bag is made specifically for side-sleepers, which, as it turns out, is a lot of us. With a centered zipper, extra insulation in high-pressure areas, and a Spoon-shaped fit designed to move with you if you switch sides mid-slumber, the Sidewinder is intended to give you the best night’s side-sleep you’ve ever had outdoors.

In theory, this lightweight sleeping bag is exactly what you’ve been waiting for all these years. But just how does it perform when you get it outside?

Features

Side-Sleeping Fit

Tossing out the idea of using a left or right-handed zipper, the Sidewinder sports a centered zipper, making it easy to get into and out of the bag regardless of which side you’re sleeping on. This feature also ensures that you won’t be laying on an uncomfortable zipper all night. Big Agnes built the bag with a Spoon Shape that widens at the shoulders, hips, and foot box to give you more room to maneuver and to accommodate legs stacked on top of each other. And these proportions are designed to move with you if you toss and turn at night, meaning you won’t just roll around inside of your bag or wake up with it twisted all around you.

Body-Mapped Insulation

Every side sleeper knows that while camping, you’ll inevitably wake up with numb hips or feet from the added pressure of sleeping on your side. Most lightweight down bags are filled entirely with down insulation, which compresses readily. While this is a great feature for packable sleeping bags, it doesn’t bode well for side-sleeping comfort. In the Sidewinder, Big Agnes added a layer of less compressible, synthetic insulation along with the 650-fill Downtek down insulation at the hips and feet for additional padding. Since synthetic insulation isn’t as compressible as down, it cradles your hips and feet in a comfortable cushion, ensuring you won’t feel the hard ground underneath. This not only reduces unwanted pressure points but gives you additional warmth right where you want it. Downtek is also hydrophobic, so the down keeps its loft even if your tent gets damp overnight.

Size and Temperature Options

We tested the down-and-synthetic Sidewinder in the Regular length for a few car camping trips in the late spring and early summer, and that configuration worked well for us. The Sidewinder is currently built as a single Men’s model with a 30°F comfort rating and a 19°F limit rating, and it’s offered in Small, Regular, and Long lengths to fit users from 5ft 6in up to 6ft 6in. The water-repellent recycled polyester shell and lining carry the same finish across every size.

At the Campsite

Traditional mummy bags were designed with back sleepers in mind, and while they don’t stop you from rolling onto your side, they don’t make it easy either. Needless to say, we were excited to see what it was like to be able to sleep on our sides in a bag that’s made for the job.

As promised, the Sidewinder comes complete with an ambidextrous zipper down the center, generous legroom, and a unique fit compared to our other mummy bags. But one of the first things that grabbed our attention was the zipper. After years spent fighting zippers that get snagged on anything from thin layers to draft collars, this special zipper head was highly appreciated every time we used it.

Once in the bag, the added insulation in the hip area was immediately noticeable. You can actually feel the difference in the baffles that contain the additional synthetic insulation. On the other hand, we didn’t notice the difference in the foot box, but it's reassuring to know you’re getting extra loft for your feet as well, even if just for extra warmth.

The centered zipper was also a huge plus and had us wondering why sleeping bags continue to use left and right-sided zippers. Better yet, this design also has an additional zipper head at the bottom to let you kick a leg out if things get too hot at night. We were a little disappointed that it’s only a ¾-length zipper instead of a full-length zipper, but it’s not enough to be a deal breaker.

Overnight, the bag performed just as you’d hope. It stuck with us as we rolled from side to side, eliminated the usual pressure points, and importantly, was incredibly easy to get into and out of, even when we were half asleep.

What We Like

• Body-Mapped Insulation This is a huge bonus for any side sleeper. For those of us who like to stay on one side throughout the night, not waking up multiple times with a numb hip makes a noticeable difference. That plus the benefit of toasty warm feet makes this one of the most valuable additions to this sleeping system.
• Patterned Fit When we read that Big Agnes designed this specifically to be able to stay with you if you toss and turn at night, we weren’t sure how different that would be from a standard mummy sleeping bag. But after putting it to the test, it makes a difference. Our standard mummy bags were a bit too loose and, more often than not, we ended up facing the inside of our bags at some point during the night.

• Anti-Snag Zipper Other sleeping bags might claim to have an anti-snag zipper, but this is the best we’ve ever seen. You have to try to get the draft collar stuck to get it to snag at all. This makes it a whole lot easier to answer the call of nature in the middle of the night.

What Could Be Improved

• Foot Box If you have big feet, you’re probably going to feel a little restricted by the foot box. It won’t make it impossible to sleep, but you’ll have to get your feet in a specific configuration and stay that way. And while Big Agnes did make the foot box slightly larger in this bag than in their mummy bags, we think a little more room would be an improvement.
• Shoulder Insulation We love the idea of the body-mapped insulation so much that we’d like to see it expanded to include the shoulder area as well. Hips and shoulders take the brunt of the pressure while side-sleeping, and we still found ourselves waking up with a numb arm every once in a while. This would add a bit more weight and bulk to the Sidewinder, but we think the benefits would outweigh the drawbacks.

• Pillow Barn We’re generally big fans of Pillow Barns, but this one isn’t executed as well as the versions found on some of the other Big Agnes sleeping bags. You can only access it through two small pockets inside of the hood, which are too small to fit an inflated pillow through. This means you have to put your camp pillow into the Pillow Barn and then inflate it, which doesn’t work for every camp pillow. It’s also hard to find these pockets in the middle of the night to shift your pillow from side to side if you decide to roll over.

Big Agnes Sidewinder Specs

Spec	Detail
Best Use	Backpacking, Camping
Temperature Rating	30°F Comfort / 19°F Limit
Weight	Small 2lb 4oz / Regular 2lb 7oz / Long 2lb 11oz
Fill	650-Fill PFC-Free Downtek Down (14oz), Synthetic (6oz)
Shape	Spoon
Fits Up To	Small 5ft 6in / Regular 6ft / Long 6ft 6in
Compressed Size	Small 9.5 x 8in / Regular 10 x 8in / Long 10.5 x 8.5in
Gender	Men’s

How the Sidewinder Compares

If you like the side-sleeper concept but want to see how the Sidewinder stacks up against other spoon-shaped bags on the market, here’s how it compares to two of NEMO’s Endless Promise bags.

Bag	Gender	Temp Rating	Weight (Regular)	Fill	Shape
Big Agnes Sidewinder	Men’s	30°F Comfort / 19°F Limit	2lb 7oz	650-Fill Downtek Down + Synthetic	Spoon
NEMO Disco 15 Endless Promise	Men’s	27°F Comfort / 16°F Limit	2lb 14oz	650-Fill Hydrophobic Down	Spoon
NEMO Disco 30 Endless Promise	Women’s	31°F Comfort / 21°F Limit	2lb 7oz	650-Fill Hydrophobic Down	Spoon

Big Agnes Sidewinder 20 Down Sleeping Bag

NEMO Disco 15 Endless Promise Sleeping Bag - Men’s

The NEMO Disco 15 Endless Promise is the warmest version of NEMO’s best-selling Spoon-shaped bag, built from fully recycled, fully recyclable materials with a PFAS-free DWR finish throughout. Thermo Gill vents let you dump heat quickly if the Sidewinder’s side-sleeper fit is what draws you in but you want a lower comfort rating for colder trips.

NEMO Disco 30 Endless Promise Sleeping Bag - Women’s

For a lighter, warmer-weather option in the same family as the Men’s Disco, the NEMO Disco 30 Endless Promise is NEMO’s lightest Disco build, with a 31°F comfort rating, 650-fill hydrophobic down, and the same Spoon shape and Thermo Gill venting as its Men’s counterpart. It’s the pick for side sleepers who want a three-season bag without the extra weight of a colder rating.

Conclusion

This Sidewinder has a lot going for it, and not just because it’s unique. For a relatively lightweight and packable sleeping bag, Big Agnes managed to keep the price reasonable. They packed it full of features that side sleepers will love, and it’s just as comfortable if you choose to sleep on your back.

With that said, who should buy this sleeping bag? Any new piece of gear has an environmental impact, not just a financial one, so we don’t think it’s worth ditching a perfectly good mummy bag for this new design. But if you’re due for a new sleeping bag and you’re a side sleeper who needs a solid, all-around bag, we’d strongly recommend putting the Sidewinder at the top of your list.

Frequently Asked Questions

Is the Big Agnes Sidewinder good for side sleepers?

Yes. The Sidewinder is purpose-built for side sleepers, with a centered zipper, a Spoon shape that moves with you overnight, and body-mapped synthetic insulation at the hips and feet to cut down on pressure points.

What temperature rating does the Big Agnes Sidewinder have?

The Sidewinder carries a 30°F ISO comfort rating and a 19°F ISO limit rating. Comfort rating reflects a temperature at which most sleepers stay warm, while the limit rating reflects the lower bound for a warm sleeper in a curled position.

How much does the Big Agnes Sidewinder weigh?

Weight ranges from 2lb 4oz to 2lb 11oz depending on size. The Small weighs 2lb 4oz, the Regular weighs 2lb 7oz, and the Long weighs 2lb 11oz.

Is the Big Agnes Sidewinder available in a women’s fit?

Not currently. The Sidewinder is offered as a single Men’s model in Small, Regular, and Long lengths. Side sleepers looking for a women’s-specific fit may want to look at the NEMO Disco 30 Endless Promise, which also uses a Spoon-style shape.

What makes a Spoon-shaped sleeping bag different from a mummy bag?

A Spoon shape widens at the shoulders and hips compared to a standard mummy bag. That extra room lets you sleep on your side comfortably while keeping the packability and warmth-to-weight ratio of a mummy-style cut.

How does the Big Agnes Sidewinder compare to the NEMO Disco 15?

The Disco 15 has a warmer comfort rating but weighs about half a pound more. Both use a Spoon shape and down insulation, but the Sidewinder adds synthetic insulation at the hips and feet specifically for side sleepers, while the Disco 15 relies on down alone with Thermo Gill vents for temperature control.

Is the Big Agnes Sidewinder good for backpacking?

Yes. At 2lb 7oz in the Regular size with a compressed size of 10 x 8in, the Sidewinder packs down small enough for backpacking trips, though it’s just as comfortable for car camping.

Does the Big Agnes Sidewinder include a stuff sack?

Yes. Every Sidewinder ships with both a storage sack for home and a stuff sack for compact transport in a backpack.

About Campman

Campman is an outdoor retail store located in Salt Lake City, Utah, that specializes in gear and equipment for camping, skiing, backpacking, climbing, and everything in between. We understand that the difference between a bad memory and the adventure of a lifetime can come down to the gear you take with you when you head outdoors, and we want our customers to have the best experiences possible. When it comes to getting outside, we get it, and we’ll get you the gear you need to get there.

Questions? Feel free to contact us by phone at (801) 999-8117 or by email at sales@campman.com.

About the Author

Dan Goodman

Most of the year, Dan can be found chasing the best climbing conditions he can get his hands on, and in the dead of winter, he'll settle for chasing powder on his snowboard. He's constantly seeking out better gear, testing new climbing shoes, backpacks, sleeping bags, and more to make his life in the outdoors a bit more comfortable. When he's not outside putting his gear to good use, he's writing about the products that he knows best.