No trade-offs here. Most ultralight bags cut corners on comfort (think half-length zippers and claustrophobic dimensions). But Marmot's 15-degree Plasma breaks the two-pound mark—the average 15-degree down bag weighs two and a half to three pounds—and still works in a full-length zipper for easy egress and better venting on steamy nights. Impressive? That's an understatement. The Plasma is stuffed with insanely lofty, 900-fill down—packed into long, weight-saving vertical baffles— and wrapped in Pertex's Kleenex-thin but Kryptonite-tough Quantum fabric. The result practically floats off the tent floor, weighing less than a liter of water and packing down to about the size of a Nalgene, yet it features a roomy cut that didn't restrict our beefiest testers. From Massachusetts's Mount Greylock to Oregon's Deschutes River, our team lauded the efficient, snug-fitting hood and silky feel. After an 18-day Grand Canyon trip, one tester likened the Plasma to snuggling into his favorite Spidey Underoos. When he was six, we presume. 15º; 1.8 lbs.
Compressibility: 5 (out of 5)
Warmth-to-weight ratio: 5