The Patagonia Nano Puff Vest earns its place as the layer that goes everywhere without taking up space, the one stuffed into a pack for a shoulder-season hike or folded into a carry-on for a trip where the weather is unpredictable. It disappears into a bag until the temperature drops and it's needed, and the regular fit sits cleanly over a base layer without bunching under a shell. What Our Gearhead(R) Experts Are Saying:"I reach for this when the morning is cold but the trail will warm up fast. The PrimaLoft Gold packs small enough to stuff into a daypack and pulls back out without a second thought."