Mountain Equipment Firefly

Lightest Mummy

Brand: Mountain Equipment

Model: Firefly

Our take If you want quilt-like weight but prefer traditional sleeping bag construction, you’ll need the lightest materials and most efficient shape. That’s what the Firefly has. The bag’s shell is so thin we could count the individual goose down plumes through the translucent, 10-denier nylon. That wispy shell, along with 800-fill feathers and a trim cut, bring this bag down to just 1 pound and 4 ounces. But it might be just a tad too light: Testers wished the footbox was a bit warmer when temps dipped into the low 30s. Svelte testers praised the slim dimensions of just over 58 inches circumference at the shoulder, but stockier testers felt claustrophobic when the bag’s three-quarter-length zipper was fully closed.

The details The seven-baffle hood has nearly twice as many chambers as is typical, which translates to a fit that feels like an oversized, comfy parka (one tester said it was the best-fitting hood she’d ever used). The bag comes with a waterproof stuffsack, an unusual bonus.

Trail cred “I tested this for five months in every kind of condition,” says an Oregon tester. “One trip we’d be sleeping under the stars on volcanic rock outside of Bend, and the next we were down in Joshua Tree, a place that’s notorious for chewing up gear. Despite the ultralight materials, the bag held up well.”

When you buy something using the retail links in our stories, we may earn a small commission. We do not accept money for editorial gear reviews. Read more about our policy.

Trending on Backpacker