Best for summer

Plusses: Super light, good value, waterproof compression sack.

Minuses: Zipperless design reduces versatility. 

Features: This is a minimal ultralight mummy bag with no zip and a basic hood. It’s made with light 15 denier Pertex Quantum fabric and Macpac’s water-resistant down. 

Fit: My 1.76m frame fitted comfortably inside the standard size, but anyone taller would better fit a large. It’s a basic-shaped bag with a gentle taper. The foot box is minimally shaped to save weight, but didn’t feel restrictive.

Comfort: The top opening is wide, to compensate for the zipperless design, and it’s easy to slide in and out. The hood has dual elasticated drawcords that cinch down to a small hole; useful if you push the bag’s limits. Extreme weight savings often force compromise – this bag can’t be opened on warm nights and has little range for cooler weather.

In use: Like its namesake, the Firefly is tiny – and once jammed inside its nifty compression bag it takes up little space in a pack. I found it excellent for sub-alpine summer use, and appreciated its low weight. Adventure racers, thru-trampers and bikepackers could consider it as a specialist lightweight bag, but not as a main bag. 

Value: Evaluating fill type, temperature rating and overall weight and size, this bag is good value.

Verdict: If you’re going this light with a sleep system, a quilt will provide more warmth for the weight, but the Firefly can be paired comfortably with another bag for winter use, and it has a hood.