Although the topbag has a comfort rating of 0 degrees C it is very minimalist in terms of features :- no zip, no hood and no down insulation on the underside. If you want the absolute minimal then this is it - personally for an extra 65g I would choose the Cumulus Quantum 250. The Quantum Top Bag has 200g of down on top and round the foot plug and only a single layer of Quantum fabric on the base. It is designed to be used on adventure races, mountain marathons and minimalist backpacking trips in conjunction with an insulating pad that is best cut to the shape of the bag (or for the hard core use bubble wrap!) Quantum Topbag - “Used by every top mountain marathon competitor, this was our chosen sleeping bag when winning the elite course on the Original Mountain Marathon in 2006. The box wall construction eliminates cold spots, making it far warmer than a similar lightweight stitch through bag with down all around.” Al Powell, Alpine Guides International Weight 430g Comfort 0°C Dimensions 195 x 75cm Pack size 15 x 24cm