The Kelty Cosmic Down 0 is a semi-rectangular sleeping bag rated to a tested comfort temperature of -8°C and a limit of -16°C, using EN/ISO 23537 lab testing rather than an unverified manufacturer estimate — a more trustworthy figure for planning cold-weather trips. Insulation is 550-fill-power hydrophobic duck down (1.12 kg of fill), treated to resist moisture better than untreated down, backed by a DWR-treated recycled 20D nylon shell and recycled 50D polyester liner.
At 1.93 kg it is heavier than down bags built with higher fill power, reflecting its budget positioning within Kelty's down lineup, but it doesn't skimp on warmth-retention details: trapezoidal baffles reduce cold spots compared with simple sewn-through construction, and a full draft collar plus draft tube seal both the neck and zipper. An internal pocket and included stuff sack round out the features. Rated for users up to 182 cm, it suits 3- to 4-season backpacking where the weight penalty is acceptable in exchange for genuinely tested cold-weather performance.