Vest choices

I have a Montbell UL Down Inner Snap vest and really like it. It packs down incredibly small and adds a good amount of warmth for the weight. My layering system is as follows: Mountain Hardware T-Shirt, Marmot Ion, Montbell Snap Vest, Montbell UL Thermawrap Jacket and a Simms Pac-Lite jacket. (Simms is a fly fishing company and made a great jacket at around 11 ounces.) I'm comfortable down to 5-10 degrees.

If you really want to get down to 5-10 degrees you'll need to get the thickest vest you can find with the layers you're considering. The Western Mountaineering Flight seems like a good idea. Montbell makes a two similar products called the Neige and Alpine down vests. But they're heavier than the WM. The others seem too thin for my taste. But I get cold easily.

Regarding sizing, I can't help. I'm renowned for purchasing clothing too large or too small.

I can't find much anywhere on how much loft it give you or how warm it is. Can anyone chime in on this?

Also, 2 people in the reader reviews had to size down one size. Have other people had to do this? I am normally an XL.

If you can afford it the Nunatak Skaha Plus Down Vest is great. It's listed at 7.5 oz for XL; if you didn't want the hood you'd be under your target (or you could reduce the fill by an ounce). I also have a MB UL Down Inner Parka (sleeves and hood) and based on that I think you'd be chilly at 5 F with one of its vests.

It is a shame Pata beefed up the new Puff vest. I have the older 6 oz micropuff version and it has been great. If you look around enough I bet you could find one on clearance somewhere online.

I personally like a vest made of down for the obvious reasons of highest warmth/weight/volume ratio. But, I also realize that a down vest is limited to camp when there is no chance of prepiring and will be covered by a more weather-proof outer jacket.

I use a down vest as a "booster" to a synthetic jacket that I will take anyway (usually a Patagonia Micro-Puff). I generate enough heat while hiking to avoid having to carry an "arctic expedition" weight synthetic and the down vest adds that extra warmth that I need for camp for neglible weight and volume penalty.

However, I wouldn't recommend a down vest while moving or as a unprotected, primary insulation layer.