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Gear Review: The North Face Mercurial Sleeping Bag Liner

Crank up your bag's temperature rating by 10 degrees with this liner.
gear guide 2010 TNF mercurial liner 445x260The North Face Mercurial Liner (BP Photo Department)

Add 10°F
Got a bag you like already, just need a little more warmth? Give it a boost with the Mercurial Liner—a wide, semi-rectangular insert that also works as a standalone bag for warm summer nights. “The Liner was a trip-saver when a late-summer thunderstorm swept in chilly air,” said a thankful tester after a trek in the mountains above Snowmass, Colorado.

The sack is made of fleece lined with nylon, and it can be used nylon-side-in (adds about five degrees of warmth, but feels clammy against the skin) or fleece-side-in (for a 10-degree boost). The long zipper goes halfway around the bag’s perimeter and adds a few ounces to its overall weight, but it also enables fine-tuning warmth and quilt-style use. By itself on warm nights (think East Coast and Southwest summers), the Mercurial is far more comfortable than a stuffy insulated bag.

“Feels more like my bed sheets back home,” says one tester. The nylon shell doesn’t repel moisture, but the material dries almost instantly. A fleece-lined stuffsack transforms into a pillow when turned inside-out and stuffed with clothes. Packed up, it’s about the size of a roll of paper towels. Caveats: It’s heavy, and we wish it came in a mummy shape, for a better fit inside our favorite bags. $99; 1 lbs. 10 oz; 50°F

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