I’ve built and slept in snow caves before. Not frequently. But I’ve done it enough to feel like my sleeping bag and I can handle the cold. So I’d never put much thought into buying a sleeping bag liner. If I could handle a night in a snow cave without extra lining, why would I need one at all? The Cocoon Merino Wool Mummy Liner has changed my mind. And not just because I first tested it on a particularly cold January night.

Cocoon Merino Wool Mummy Liner

The first night I used my Cocoon Merino Wool Mummy Liner, the nighttime low was 18°. We were camped near a lake, and the wind was whipping off the water toward us. I can’t say I was toasty warm inside the liner that was in my bag that was in my tent. I can say I was glad I had that extra 12.6° F.

Now that it’s part of my camping gear, the Cocoon Merino Wool Mummy Liner is like a favorite fleece pullover. Even if the temperatures are going to be tolerable, slipping inside that liner at the end of a hike is even more comfortable than sitting around a campfire.

But the real reason I’ve converted to the Cocoon Mummy liner comes anecdotally from one of my co-workers. As a Scout Master who spends even more time on the trail than I do, he was tired of having to buy a new sleeping bag every few years. But since he began using liners, he’s seen the life of his bag extended. According to him, a hundred-dollar liner is a better deal than a three hundred dollar bag every couple of years. And he’s currently using the Cocoon Merino Wool Mummy liner, too.

Good to know it’ll be more than a few years before I have to buy a new sleeping bag.

Cocoon Merino Wool Mummy Liner


  • An extra 12.6° Fahrenheit. That’s the added temperature rating it claims to give your sleeping bag. (That’s +7.0° for you Celsius-types.) That’s a lot of extra warmth for something that doesn’t add much weight to your pack.
  • Very comfortable without any constriction. Very soft and stretchy.
  • Extremely lightweight.
  • Avoids odor and and is germ-free. (I’m taking Cocoon at their word on this. I haven’t had it long enough to verify its odor-avoidance qualities.)
  • Theoretically, it extends the life of your sleeping bag.


  • Price. At $99.95, it might be a shock that something so lightweight and flimsy-feeling would cost so much. Some might be tempted to rationalize putting that extra hundred towards the price of a warmer bag.
  • Difficult to buy direct from the manufacturer. At the time of writing, the US website is under construction.





Manufacturer: Cocoon
MSRP: $99.95
Listed Weight: 17.5 oz. (495 g)
Materials: 100% wool.
Colors Available: black


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