Mountain Hardwear Expander
Mountain Hardwear Expander (courtesy, REI)

Can I add girth to my sleeping bag?

I'm sure that you don't have this problem, but some of us are a bit bigger around than most sleeping bag manufacturers think we should be. I've seen expanders that claim to add six to ten inches to a bag's girth. Do they work, or should I just hunt till I find a bag that fits out of the box (so to speak)? Joe Raleigh, North Carolina

Mountain Hardwear Expander

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Let’s face it, whatever one’s girth, sleeping in a classic “mummy” bag isn’t always a fun experience. Skinny sleeping bags are designed to, A) save weight, and B) conserve warmth. At-home-king-sized-bed comfort does not fit into that equation.

Mountain Hardwear Expander Mountain Hardwear Expander

So what to do? As you note, Joe, several companies make “expanders,” which attach to a bag’s zipper and act like a big gusset. Mountain Hardwear, for instance, sells what it calls simply the Sleeping Bag Expander ($55;, which is a down-filled device that adds eight inches of girth (at the shoulders) to any bag with a number eight YKK zipper. Which is most of them. And you can use it with either a down or synthetic bag, so don’t worry about that. Big Agnes makes a similar product, called the Wedgie, with PrimaLoft synthetic fill that sells for $49 (

For that matter, if you’d rather just get a bigger bag, Big Agnes’ Lost Ranger ($199) is nearly twice as wide as most mummy-style bags. Big Agnes makes their bags with an uninsulated “bottom”—as in, you insert a sleeping pad into that area to add insulation beneath you. So the three-pound weight is not bad for a 15-degree bag. Or Marmot’s Sawtooth is an extra-wide bag (70 inches at the shoulder) made in the traditional insulation-all-around style. It’s $239, filled with down, and rated to 15 degrees ( REI’s Syn Cat bag ($119; puts wide-bag comfort into an affordable, synthetic-fill bag.

Sleep well!

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From Outside Magazine, April/May 2021
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Lead Photo: courtesy, REI