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Description
Big Agnes Sidewinder SL 20Specifically designed for those who sleep on their sides, the patent pending Sidewinder Series was engineered to ensure warmth, comfort, and ease of use no matter which side you're on. Constructed with features you expect from a traditional mummy bag with additional body mapped insulation to optimize warmth where you need it and minimize pressure points and other side effects. The Sidewinder SL is a side sleepers dream bag with technical features that
Specifically designed for those who sleep on their sides, the patent pending Sidewinder Series was engineered to ensure warmth, comfort, and ease of use no matter which side you're on. Constructed with features you expect from a traditional mummy bag with additional body mapped insulation to optimize warmth where you need it and minimize pressure points and other side effects. The Sidewinder SL is a side sleepers dream bag with technical features that roll seamlessly from one adventure to the next, and from one side to the other at night.
Features
- Specifically designed for people who sleep on their sides with a technical fit, patterned to move with you as you roll from one side to the other
- Close fitting, jacket-style hood keeps insulation close to the body without sacrificing mobility
- Keep pillow in place with unique Pillow Barn made of stretch mesh material with interior access from either side for easy adjustment
- Optimized warmth and minimized pressure points with body mapped insulation
- Improved shell fabric and lining with PFC-free water repellent finish
- Down fill with a PFC-free water repellent finish throughout the bag provides lofty warmth while synthetic insulation helps alleviate common pressure points in the hips and feet
- Optimized fit and thermally efficient footbox is patterned to mimic the shape of your foot position while lying on your side
- Smooth, quick zip with anti-snag locking zipper with no-draft zipper garage, and long, ambidextrous zipper
- Easily adjust hood without unzipping using low-profile internal cordlock access
- Seal out drafts by cinching insulated tube along upper hood opening
- Hang dry or store bags with exterior loops
- Storage sack & stuff sack included
Construction + Materials
- Shell: nylon ripstop featuring a PFC-free water repellent finish
- Lining: polyester taffeta featuring a PFC-free water repellent finish
- Primary Fill: 650 fill DownTek repels water while maintaining insulating value - bluesign Certified PFC free water repellent chemistry
- Body Mapped Fill: FireLine ECO Synthetic Insulation, 100% post-consumer recycled polyester, featuring low-denier fibers that are tightly woven and provide high loft, compressibility, high weight-to-warmth ratio, and durability
- Regular: fits up to 6' / 183cm
- Long: fits up to 6'6" / 198cm
- Works with any pad size or style
Specs + Sizing
| Bag Weight | Regular: 2lb 4oz / 1.02kgg / Long: 2lb 8oz / 1.13kg |
| Fill Weight | Regular: 19oz / 538g / Long: 21oz / 604g |
| Compressed Bag Size | Regular: 6.5" x 8" / 16 x 20cm / Long: 7.5" x 8" / 19 x 20cm |
| Stuff Sack Size | Regular: 8" x 17.5" / 20 x 45cm / Long: 8" x 17.5" / 20 x 45cm |
Shipping Notes
- Free Standard Shipping on $100+ Orders to the USA.
- Except Preorder products are shipped in 48 hours.
- Delivery to the USA:
- Standard Shipping : 3-10 business days
- If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
- We offer a 30-day return/exchange service after receiving.
- Final sale items are not eligible for returns or exchanges.
- To process your return/exchange, please contact us at [email protected]
- Please click here for more details>>> Return & Exchange Policy
4.5 ★★★★★
Based on 270 reviews
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Product Reviews
★★★★★ 5
Excellent all-poly athletic socks for general lifting and HIIT.
Size: Medium, Color: Black/White/Grey
***These are NOT “low” -cut socks as the description in the title states. These are actually “quarter”-cut socks as clearly visible in the picture of the sock itself. “Low” -cut socks are shorter than this height but still visible with a shoe. Also, on the actual UA package of these socks, it clearly states these are QUARTER cut socks.
My review: Gave these UA Performance Tech socks (UAPT) 5 stars since they’re very good but in all reality not the best socks I’ve ever had for lifting and HIIT workouts. That title goes to Nike Dri-Fit MAX socks (DFM)….but these socks are really good. Like Nike’s DFM’s, these UAPT socks come in sizes, halleluah (M, L, and XL). The idea that most athletic sock are sized 6-12 and should therefore fit everyone perfectly is absolutely ridiculous. Your shoes come in whole and half sizes…so socks should at the very least be sized like these UAPT’s and Nike DFM’s…in S/M/L or in this case, M/L/XL. I wear a men’s size 8 shoe and the M (medium) size in these socks was a perfect fit; true to size.
Also, UAPT socks are ALL polyester with Spandex which is ideal and 100% that which you want for athletic socks: wicking with stretch. Cotton socks are the absolute worst thing you could wear to the gym since they’re sponges for sweat and therefore get wet and heavy, cause blisters, tend to stink, stick to skin, etc… IF you prefer cotton socks for athletics, then you don’t understand how performance fabrics work in athletics and training. You do NOT want cotton in your athletic apparel. You want your fabrics that wick sweat away; NOT soak up sweat and hold onto it. Also, the flexibility and stretch of the foot and ankle parts of the sock were both just right. Snug but not too tight. Wicking is perfect, too. Already worn during two 3 1/2 hour workouts and my feet stayed as dry as a desert.
When looking for UA athletic socks on Amazon, I surprisingly continued to find UA “athletic” socks made with mostly cotton which completely surprised me because a serious athletic company should produce an abundance of performance-level socks… i.e. all-poly socks. Thank goodness I finally came across these UA all-poly Performance Techs. The only drawback to these UAPT’s…and it’s a minor drawback…is that unlike Nike DFM’s, these do not come in L & R (left and rights) to specifically match the individual foot shape. Nike DFM socks come in L and R which sets them apart from all other athletic socks…and yet I don’t like supporting a massive monopolistic athletic apparel company like Nike, but they’re the only one that makes THE best athletic sock.
Nonetheless, these UAPT’s are perfect workout/HIIT/lifting socks for the bundle value price of six pair and three colors. If you’re looking to match your new UA or Rock shoes with the appropriate UA athletic sock, then here you go. I chose the black/white/gray mix bundle since I have new pairs of a black and a white version of the same UA-Rock shoe. These UAPT socks are medium thickness so they didn’t take up an exorbitant amount of room in my shoes but they’re thick enough to prevent blisters and provide cushion. Overall they’re very comfortable, hold a good stretch, hold their shape, and seem to be durable but only time will tell.
And since we’re on the black and white sock subject, I couldn’t resist: I read a shoe review about someone angered that his new UA/Rock black shoes (obviously bought for casual wear in lieu of gym use) staining his white cotton socks. First of all, never ever wear white socks (much less cotton white socks) with black athletic shoes! The possibility of staining is always there and the appearance just doesn’t work. However, you can get away with black socks with white shoes in some cases…but never white socks with black shoes. Why? Who knows? It’s just one of those unwritten rules of the gym. And no, I didn’t make the rules…so don’t blame the messenger. LOL!
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Reviewed in the United States on July 28, 2025
★★★★★ 5
Very soft and wears well
Size: Medium, Color: Black/White/Grey
Very nice quality and soft
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Reviewed in the United States on April 18, 2026
★★★★★ 5
Great buy
Size: X-Large, Color: Black/Black/Black
Good socks that fit well.
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Reviewed in the United States on February 20, 2026
★★★★★ 4
Good sock
Size: Large, Color: Black/White/Grey
Great cushion and solid fit. Some days my feet are tired from the compression fit, but they do support my feet well.
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Reviewed in the United States on October 9, 2025
★★★★★ 5
Exceptional!
Size: Large, Color: Black/Black/Black
Best socks I have ever worn. Already bought more.
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Reviewed in the United States on March 31, 2026