Product Review: Big Agnes Thunderhead SL 30 Sleeping Bag

As much as we all love camping, we can’t help but notice the little nuances that may come with it. My tent smells like a wet dog, my air mattress flattens throughout the night and I always seem to cross the line between “water resistant” and “waterproof.” At the end of the day, the last thing I want stopping me from getting a good night’s rest is a loud zipper that’s snagging its way up my sleeping bag.

The Big Agnes Thunderhead SL 30 is a different breed of sleeping bag, designed to keep you warm and comfortable without the use of zippers. After you’ve slipped your legs in, it works by folding over an oversized anti-draft collar around you and inside the bag itself (imagine the sleeping bag giving you a hug). Easy to find clips keep the cocoon-style bag closed, and a one-handed cord lock lets you cinch the hood. The unique collar creates a wide opening and getting in or out of the SL 30 is quick, easy, and quiet—fit for a camping ninja.

I was skeptical as to whether a zipper-less system could retain enough heat, but to my surprise the Thunderhead SL 30 has been the warmest and most comfortable sleeping bag I’ve ever tested. This is due to Big Agnes’ DownTek, which works as fantastic insulation, and it’s designed to repel moisture. The structured walls trap body heat, and using the anti-draft collar feels like wrapping up in my down comforter at home. Although it’s rated for 30°F, I’ve only tested it down to 40° The Thunderhead was plenty warm while wearing only boxers and a light T-shirt. For colder weather, BA also offers a 20-degree version called the Pin Ears.

The SL 30 is shaped much like a mummy-style sleeping bag, but it provides more room in the hip and feet area. I toss and turn all night, so I appreciated the extra space. The Thunderhead is also equipped with a half-pad sleeve on the back to keep the bag in the center of the sleeping pad, and to help prevent you from rolling away in the middle of the night.

Big Agnes includes a mesh storage sack with the SL 30 as well as a stuff sack that compresses to 5.5 x 6 inches. The zipper-less design brings weight down to a feathery 1 lb. 12 oz., making it lightweight and an ideal for backpackers or camping motorcyclists. It’s durable too, constructed with a nylon rip-stop shell and nylon taffeta lining. While compressed, the sleeping bag will fit in most side luggage, rear cases, or backpacks.

When it comes Big Agnes products, there’s usually little to complain about, and that’s the case with the Thunderhead SL 30. Sleeping bags that use down may have issues if they get wet, but Big Agnes’s Downtek technology works to combat moisture build-up from sweat and humidity. The exterior shell also has a water repellent finish. I didn’t have any moisture issues after a straight week of camping, but for those of you concerned with down reliability, BA offers a full line of synthetic sleeping bags that generally cost less than their Downtek options. That being said, it seems like the functionality of the Thunderhead’s zipper-less, oversized collar design can only be pulled off with Downtek, since Big Agnes doesn’t offer a variant using synthetic material.

A being comfortable while sleeping is critical to having a positive camping experience. Big Agnes products have always impressed us, and this sleeping bag is no exception. If you’re ready to trade zips for ZZZs be sure to take a close look at the Thunderhead SL 30. MSRP: $249.95-$269.95 BigAgnes.com