This addition to the 2011 Editors’ Choice Award-winning Plasma line takes the best of its three-season siblings—excellent warmth-to-weight and all-around comfort—and packages it in a summer bag. Critical ingredient: Insotect’s Flow construction. The vertical baffles transmit heat more easily from your core to your extremities, and the FlowGates hold the down in place for even distribution. Combined with plush, 900-fill down, this design lets Marmot use a shape that’s less hyper-efficient than some ultralight sacks. The girth at the shoulders is 60 inches (that’s four more than the Mountain Speed’s, left), which enhances comfort, especially for big or restless sleepers.
The Plasma kept one tester warm right down to the 40°F rating in Joshua Tree National Park. Expecting milder temps? Our tester in the Channel Islands praised the breathability of the water-resistant Pertex Quantum shell, which made warmer nights (up to 60°F) quite comfortable. “It looks wimpy, but the shell is surprisingly durable,” says another tester. “We used it as a duvet while stargazing in California’s notoriously abrasive Mojave Desert, and the Plasma showed no weakness.” The contoured hood—Marmot’s superior design doesn’t use face-scratching Velcro—cinches snugly, and the full-length zipper doesn’t snag. Packed size (think liter soda bottle, just slighter larger than the Mountain Speed) is impressive. Bummer: The price is steep for a mild-weather bag. $399; 1 lb. 3 oz.; 40°F; marmot.comInsotect Flow Technology