Packing Heat: Big Agnes Flume UL 30

The Big Agnes Flume UL 30 runs true to its 30-degree temperature rating. The DownTek down is resistant to water and dries quickly, helping make this bag very packable and lightweight--perfect for bikepacking.

The Big Agnes Flume UL (photo: Aaron Chamberlain)

It’s pretty easy to come up with a comfortable sleeping arrangement when car camping. You don’t even need fancy gear: just keep adding blankets to the mix until you have a soft surface to lay on and plenty of warmth. But what about when you have to carry all your gear with you at all times like you do while bikepacking? Then things get a little tougher. After all, there’s only so much you can take with you because of size and weight constraints.

You don’t need to spend a ton of money on gear to get into bikepacking, but if you’re looking to move fast and travel light, premium gear — and its associated premium price tag — often goes with it. The Big Agnes Flume UL 30° sleeping bag is one such piece of gear.


Quality zipper with easy-to-find pull (photo: Aaron Chamberlain)

Dissecting the name, the Flume is an ultralight (UL) sleeping bag rated down to 30° F. The Flume’s light ripstop nylon shell is filled with DownTek water repellent down insulation. If you don’t know, down is the preferred insulation of most campers, hikers, and backpackers. Down is actually the tiny fluffy feathers underneath the exterior feathers of ducks and geese. Gram for gram, down is lighter, warmer, and more compressible than synthetic insulations. Traditionally, the main drawback to down is that it’s essentially useless when wet. The DownTek treatment causes the feathers to absorb less water and dry faster after being wet. Big Agnes treats the exterior of the bag with a water repellent finish as another layer of defense.

A drawstring inside the hood to cinch it down (photo: Aaron Chamberlain)

The Flume is a mummy-style bag, meaning it’s shaped like a sarcophagus, tapered sharply at the head and then gradually from the waist to the feet. There’s a single, 40-inch-long zipper on the left side of the bag, and a drawstring to cinch down the hood. I opted for the “long” size of the Flume for extra room all around. Dimensions for the long are: 62″ circumference at the shoulders, 56″ at the waist, and 38″ at the feet. The regular size Flume is 2″ smaller in each dimension. Big Agnes claims the long will fit people up to 6′ 6″ tall. My bag weighed about a pound and a half (680g).

Pricing for the Flume is $470 for the regular bag and $500 for the long. But fear not: Big Agnes offers down bags starting at a more reasonable $190 for the Boot Jack. Obviously, they won’t be as lightweight or compressible as the Flume, but you still get the benefits of DownTek.

On the Trail

The Flume packed away neatly into my seat bag and kept me toasty when camping at high elevations (photo: Aaron Chamberlain)

When I rode the Steamboat Ramble back in July, the organizers graciously lent me camping gear so I didn’t have to fly with my own. Since Big Agnes is a sponsor of the event, it’s no surprise that the tent, air mattress, and sleeping bag came from them. The tent was easy to set up and the air mattress was plenty comfortable, but it was the Flume sleeping bag that stood out most.

On our first night out we camped at Red Feather Lakes around 8,000′ in elevation. The overnight low dipped into the low 30s, but I stayed nice and warm inside the Flume. I found the bag plenty roomy even when completely zipped up, but I’m not particularly claustrophobic, either. In fact, I could roll over and sleep on my side inside the bag without the entire bag rotating with me. The spacious interior meant I could stuff my pillow inside the hood, and it stayed put. A techy fabric pillow sandwiched between a techy fabric air mattress and a techy fabric sleeping bag is usually a recipe for slipping and sliding — not so with the Flume.

The Flume comes with a large bag for long-term storage as well as this stuff sack (photo: Aaron Chamberlain)
Putting it in a compression bag let me really minimize the Flume’s volume (photo: Aaron Chamberlain)

After the Ramble, I got in touch with Big Agnes to get a Flume of my own. The bag has since accompanied me on several camping trips as well as the Cohutta Cat bikepacking route. The bag’s diminutive size and heft helped keep my overall bike weight low and left plenty of space for extra gear. I have a couple other sleeping bags, including a nice Kelty down bag and a midrange Marmot synthetic bag, but neither could match the Big Agnes in terms of weight or packability.

The Cohutta Cat was alternately warm and sunny, then cold and rainy. Unfortunately, the cold and rainy parts came at night when I had to set up camp and sleep. I got the Flume into the tent quickly in an effort to keep it as dry as possible. The exterior of the bag got a little damp thanks to the high humidity, but never wet enough to affect the insulation. Once I got home, the bag dried out completely with no trace of a funky odor, despite being stuffed into a seat bag while damp for three days.

Finish Line

One possible negative feature of the Flume: the zipper only goes down to about your waist. It doesn’t extend the entire length of the bag, which might be a deal-breaker for some. Personally, I prefer a full-length zipper so I can swing a leg out if I get too hot. As a result, the Flume isn’t an ideal summer bag, but it’s probably designed too warmly for that anyway.

The best way to sum up the Big Agnes Flume is to say that it’s like a really nice down jacket, but for your entire body. Its warmth is true to its temperature rating — which is surprising when you feel how light the bag is and how thin it feels — and its supreme packability make it an excellent option for bikepacking.

Thanks to Big Agnes for providing the Flume UL 30 for review.

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