Big Agnes Fly Creek UL 25° Sleeping Bag

The Big Agnes Fly Creek UL 25° is a three-season down mummy bag in Regular size, weighing 722 g with 482 g of 850-cuin down treated with a PFC-free hydrophobic finish. EN/ISO 23537 testing puts it at 2°C comfort and -4°C limit, and the draft collar plus draft tube around the half-length zip cut the two biggest heat-leak points on a mummy bag. The 10D ripstop NetPlus shell keeps pack size and weight down. The down fill itself is RDS-certified for responsible sourcing, and the bag separately carries bluesign certification and a recycled-materials flag - three distinct sustainability markers rather than one blanket claim, none of which affects the warmth numbers above. At 722 g this sits in the ultralight three-season bracket - good for spring-to-autumn trips where nights sit around or a little above freezing, not for winter use below its -4°C limit. The half-length zip saves weight over a full zip but limits venting options on warmer nights, so pair it with a liner or wide-open top if you tend to overheat.