Fill
Fill weight: 450 g (size M)
Fill power: 900 EU (970 US) white Polish Goose down
The most important part of a sleeping bag specification as the combination of fill weight and fill power (FP) is what provides the sleeping bag's ability to insulate.
450 g of 900 FP down will fill the same volume as 505 g of 800 FP down or 575 g of 700 FP down.
Construction
Baffles: Box wall throughout
Hood: Adjustable cowl
Neck: Simple adjustable baffle
Zip: Full length #5 YKK
Zip baffle: Single
The construction describes how the down is held in place (otherwise all the down would fall to the bottom) and what features are incorporated to maximise heat retention or, conversely, regulate your temperature. A bag as light as the Firelight 450 does not need to have sophisticated features as there simply isn't enough down for it to be expected to perform in very cold temperatures (although it is certainly better than having nothing).
Fabrics
Shell: 29 g/m² 15 denier nylon (Pertex Quantum)
Lining: 29 g/m² 15 denier nylon (Pertex Quantum)
Lightweight fabrics allow the down to loft and reduce the weight of the bag. Although there are lighter-weight versions of the Pertex Quantum fabric we are using, they offer a negligible saving in overall weight and, having a lower tear strength, are easier to damage.
Bags:
Stuff sack: 25 g
Storage bag: 75 g