The Sierra Designs Men's DriDown Better Down Vest makes an excellent ultra warm, lightweight layering piece. The trim fit enables easy layering and reduces weight, while the 800 fill down provides excellent insulation for quick warmth. And you may be asking yourself, why sleeves' Well, they lock the heat in that you'd usually loose through the armholes of a vest, and the stretch underarm panels provide the same mobility you'd have in a vest. The single pull drawcord hem locks in heat, and the half zip front lets you ditch heat if you need to. Perfect for extra cold conditions, or packed away as an emergency mid layer.