it's very light and warm for the winter. fit very well as middle layer.
Very happy with my Cerium LT. First down jacket and it was everything I hoped for - cut close to the body to keep the heat in, light, very warm, all while not looking like the Michelin man. Fits easily under a shell or can be worn by itself with a baselayer down into the 30s.
Another awesome jacket from Arcâ€™teryx! Very light and packs perfectly into the pocket stuff sack. Very warm and easy to move around in.