There are two schools of expedition mitten design. No, really, there are, because... climbers! Most big mountain mitts are layered affairs. A shell holding lofty insulation, usually synthetic but occasionally down. An inner mitt, trigger finger mitt (index finger separate), lobster mitt (two and two) or glove (you should know this one). So there have always been choices, except if you wanted just a big bag of down to throw over the gloves you were already wearing, then and only then were you poopy out of luck.
No longer! Mountain Hardwear's fast and uber-light gear inspired by Ueli Steck is about as minimalist as you can get and still feel safe on a big mountain. The Nilas down mitten has no liner, just their OutDry waterproof breathable shell packed with oh-so-lofty 800 fill down. They weigh in at under six ounces - yes, you read that right - and their only features are a nonslip palm and a cordlock cuff. Brilliant, we say.
The Nilas mitt is sized to go on over a thin to medium sized liner glove, so if you want them to wear over a beefy guide-style glove you may want to size up. Either way, the Nilas mitt is so light and packs so small it will disappear into your pack, ready when you need it. A great solution that fills a major gear gap.