For that, however, you get 900gsm of 600 fill power duck down, making the bag lofty, comfy and a joy to sleep in. In our experience, we’ve comfortably slept in this thing in nothing but baselayers down to -5 or -6 degrees Celsius, though we wouldn’t push it further than that without a liner or without wearing a warm jacket inside. We’d bet that you’d see the Leviathan’s unmistakable off-yellow hue emanating from at least a quarter of them.

Additionally, the reasonably small pack size and weight of this bag make it a solid all-rounder for numerous adventures. As he got older, the hills got bigger, and his passion for spending quality time in the great outdoors only grew - falling in love with wild camping, long-distance hiking, bikepacking and fastpacking. Very light, good product, but it broke when I used the zipper for the first time, which made me unable to close the quilt all night. In general, then, fill power is a useful marker for understanding how much down you might need to achieve the same insulatory effect.The compression stuff sack lets you pack it down to a very compact and manageable size for packing and carrying. Hell, just head into the Lake District in mid-January and take a peek into the various tents you spot. I’ve had the OEX Leviathan EV 900 for a few years now, and I’ve slept in it at varying temperatures in different climates.

The 900gsm / 600 Fill Power duck down in the Leviathan has a fluorocarbon-free hydrophobic coating, which helps it to retain loft when it gets damp, performing better than untreated down.When it comes to packing away, the compression stuff sack will save room in your pack until you get home, where you can switch to the breathable mesh sack to help the down decompress to maintain its performance on your next adventure.