What They say:

A sleeveless version of the all-around, everyday Aconcagua Jacket, this is a great vest for layering during cold-weather or a standalone piece in tepid conditions.

• Brushed internal collar
• Two hand pockets
• Hem cinch cord

• Avg Weight 494 g (17.4 oz)
  
• Length from Center Back 28 in.
  
• Fabric body: 40D 58 g/m2 (1.7 oz/yd2) taffeta woven nylon with DWR
  
• Fabric insulation: 550 down fill

What GearGuys say:

It's amazing how much difference just a down vest can make on a cold day.  Keep the core warm and everything else seems happy.  Vest's make great traveling companions too.  Highly packable, they won't take up too much space and can save you when the day turns foul.  For uber warmth, check out the Nuptse vest.