722g / -4°C

Best for 

Three-season through-hikers and climbers who prioritise weight and packability.

Overview

This streamlined bag combines a minimal mummy design with high-performance materials to maximise warmth-to-weight. Diamond Quilting baffles contain 482g of 850-fill Downtek water-repellent down, while the shell and liner fabric use recycled NetPlus 10D ripstop nylon with a water-repellent finish. It has an adjustable hood, a draught collar and a half-length zip, and is rated to 2°C comfort and -4°C limit. The fabric and fill are PFAS and PFC-free and the bag is available in regular or long. 

Performance

This bag’s dimensions suited my average height and lean build well, although some people might find the foot box constrictive. The half-length #3 nylon coil top zip is a weight-saver but limits ventilation. However, if it’s warmth you crave, although the neck baffle is minimal, this bag’s slim outline minimises dead air, and the close-fitting hood cinches tightly to trap air when you are pushing the temperature rating. Water-repellent down and impressively water-resistant fabric make it very reliable for sustained wet weather or sleeping under the stars. The 10D fabric is at the low end of durability and could be a concern at a rocky bivouac, and this size of zip does tend to catch more. However, I’ve spent 100-plus nights in a bag with the same weight of zip and it still works well.     

What we like

Impressive warmth for weight, excellent water repellence, light and packable.

Limitations

Poor ventilation and small footbox, durability of 10D fabric, expensive.

Why buy the Fly Creek UL 25? 

Its svelte silhouette and pared-back features optimise warmth for its weight, and once squashed with a compression stuff-sack it’s certainly a space saver in your pack. While there are other premium bags with similar specs that are cheaper, it’s hard to find one as warm or as water-resistant for the weight.