Model: Altitude Spring
It packs down as small as a summer bag and weighs just two pounds, so testers greeted this mummy with skepticism: Few dared to take it to its 15°F limit. But the Alpini wowed the ones who did. “I stayed warm at its rating, and would trust it down to 5°F,” reports one tester who used it during a snow-cave campout at 10,000 feet in Colorado’s Park Range.
The Alpini achieves its impressive warmth-to-weight ratio with 850-fill down sandwiched between ultralight, 15-denier Pertex Quantum fabric. Plus, offset baffles stagger the stitching on the outer and inner shell to prevent cold lines on the seams. The draft tube running along the full-length zipper uses two seams instead of one to create a fat U shape that effectively traps heat.
The hood is “snug but not confining, so I warmed up fast without feeling stifled,” reports one tester, and the opening is trimmed with a down-filled tube (instead of an elastic band), which feels softer than elastic and helps further trap warmth.
Durability is excellent; we dragged it over rocks and sharp tundra grass in Iceland’s Hornstrandir Nature Reserve, and the Alpini never snagged or lost a feather.
Bonus: A tiny interior pocket holds lip balm. Caveat: Side-sleepers and big guys found the hyper-efficient cut a bit tight.
$369; 2 lbs.
15°F; reg. and long;
Mammut’s down bag for warmer climates. Completely re-designed for Summer 2009, the Altitude Spring features advanced baffling construction to eliminate cold spots, a Hot Head Hood for maximum head protection from the cold, and a differential cut to save weight, improve loft and increase insulation capacity.
Construction: Advanced Baffling
Fill: Goose Down-800
Fill Weight: 260g / 240g
US Temp. Rating: +25F