Chamber structure allows down's optimal expansion and reduces heat loss
Mummy-like shape for better thermal comfort and unconstrained movements
Long zipper allows ventilation and fastening the sleeping bag with another one 
Anatomically profiled hood provides comfort for you head
Inner collar allow separating the torso part in order to give better thermal comfort
Velcro fastener to close or open the collar
Inner pocket
Insulating down slat along the zipper keeps the warmth in.