Big Agnes Sidewinder SL 20
Summary
Price At Time Of Writing | $399.00
Our Overall Rating | 80 out of 100
Pros - Perfect for side sleepers, warm, roomy
Cons - Down shedding, not for back sleepers
Overall - A backpacking tent for cold conditions
Technical Specifications
Packed Size - 20x44cm
Weight - 1.02kg
Fill - 650 DownTek™ and FireLine™ Eco
Our Analysis & Ratings
If you're the kind of sleeper who tosses and turns all night, only to wake up tangled in a twisted mess of fabric, the Big Agnes Sidewinder SL 20 is about to become your new best friend. This bag is designed specifically for side sleepers who roll from one side to the other, so you stay cosy and comfortable no matter how much you move. Big Agnes even offers the same bag in a warmer 1.7°C version and a longer size, giving you options depending on your needs.
Comfort - The mapped insulation stays put whether you're on your left or right side, keeping you warm without any awkward gaps. It feels great whether you're wearing layers or just sleeping in your underwear, and even though it's a mummy-style bag, the footbox doesn’t feel tight or restrictive. The only small downside? If you end up lying directly on the hood, it can bunch up in a weird way.
Construction - The Sidewinder SL 20 takes the classic mummy shape and tweaks it just right for side sleepers. Both the shell and lining have a PFAS-free water-repellent finish, and the down is treated to resist moisture too. The outer shell is made from durable nylon ripstop, while the lining is soft polyester taffeta. The only minor issue is that the inner down can shed a little over time, which might be annoying if you’re super particular about maintenance.
Features - The snug, jacket-style hood keeps heat in and it even has a stretchy mesh panel to help hold your pillow in place, so no more waking up to find it slid across the tent. The anti-snag zipper has a no-draft tube to block cold air, and the hood has extra insulation to seal out chilly drafts. There are also exterior loops for hanging or drying the bag and it comes with a stuff sack, though you might want to swap it for a smaller one if you're trying to save space in your pack.
Size/Weight - The size and weight are pretty impressive. It’s 1kg, which is light enough for backpacking, and it compresses down pretty small. The included stuff sack is roomy, so if you’re trying to pack ultra-light, you could easily fit it into a smaller compression sack instead.
Versatility - This is a great three-season bag, perfect for spring, summer and fall trips. You’d definitely overheat if you tried using it in warm weather and on bitterly cold winter nights, you might need something with a lower temperature rating. While it’s not the absolute lightest bag out there, 1kg is still reasonable for most backpacking trips unless you’re counting every gram.
Overall - The Big Agnes Sidewinder SL 20 is a fantastic choice for side sleepers who camp in moderate to cool weather. Whether you’re backpacking or car camping, it keeps you comfortable without the usual twisting and tangling. It’s not built for deep winter, but for three-season adventures, it’s one of the best options out there for restless sleepers. If you’re tired of fighting your sleeping bag all night, this one’s worth a serious look.
