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The Firelite is part of Mountain Equipment’s 'Extreme Light' range of sleeping bags. Mountain Equipment state that these are the lightest, most efficient sleeping bags they have ever produced.

The Mountain Equipment Firelite uses 469g of 90-10 800 Fill Power Russian goose down in an ultralight 10D outer shell. The shell is made from their own Plasma 10D fabric which is also supposed to be highly breathable and exceptionally tear resistant for its weight. My first impression on taking the sleeping bag out of the storage cube was how well constructed this bag feels, it oozes quality. The fabric feels incredibly light but not fragile and I never felt it had to be treated with extra care compared to other heavier bags I’ve used. The bag lofts brilliantly when unpacked – it’s always so satisfying the way top quality sleeping bags expand when removed from their stuff sack. This loft is aided by the ultralight shell fabric which lets the down expand without weighing it down.

Mountain Equipment employs an expert in down technology (they call him Dr Down because he has a doctorate in down technology!). The latest innovations from Dr Down have been put into action on the Firelite including the EXL system – lightly elasticated internal seams in the top half of the bag to reduce drafts, dead air space and to pull the fabric away from the down for maximum loft. You hardly notice the EXL in practise so any fears that it will make the bag feel tight are soon lost once you use it. EXL definitely does work though. I move around a fair bit when I sleep which often sucks cold air into the bag but the EXL system stopped this while still allowing me to move comfortably.

A traditional shoulder/neck baffle has been replaced with a lighter collar baffle and slanted box wall baffles are used to save further weight from the sleeping bags structure.

When I first saw the Firelite, my initial thought was that its fitted mummy shape might feel a bit restrictive. I often switch between sleeping on my back and side during the night and so a bit more room is often required. When you first climb into the Firelite it feels snug, helped by the EXL system and very much a ‘mummy’ bag but I found it extremely comfortable. I was able to move from my back to my side with no problem.

Mountain Equipment are taking the ethics of their down sourcing very seriously. You can check the provenance of the down used in your bag using their Down Codex system. This has details of the quality of the down, it’s make up and the details of the farm for every bag. The down in this Firelite exceeded the stated 800 Fill power with a result of 835 for the batch of down used. In the case of the Firelite that I used here is an example of the information available –

Your Down Content & Fill Content Down

• Cluster 91.1%
• Down Fibre 2.2%
• Feather 6.6%
• Other 0.1%
• Fill Power 835

The Firelite has an EN Comfort Limit rating of -6C but Mountain Equipment prefer to use their own ‘Good Night Sleep Guaranteed’ rating which is -9C. The EN sleeping bag test is flawed for bags suitable for colder conditions, so ME base their own rating on extensive testing both in the field and thermal imaging analysis in cold test rooms at the Leeds Beckett University.

On one night, the temperature was so cold that my breath froze as a sheet of ice around the collar of the bag. I can’t say for sure what temperature it was but I would estimate in the region of -6 or -7C. In combination with a Thermarest NeoAir Xtherm, the Firelite kept me warm all night. I slept wearing light base layers and was quite shocked when I discovered how cold it was in the morning. I would say that Mountain Equipment’s own rating definitely stands up from my experience.

The hood design was extremely effective and was a big factor in contributing to staying warm when the temperature dipped down towards the limits of the bag.

Mountain Equipment supply a ‘storage cube’ to store the bag in between trips without compressing the down and a waterproof roll top dry bag/ stuff sack. I must confess I didn’t use the supplied stuff bag. I used a Sea To Summit Ultra-Sil Event Compression dry bag to reduce the pack size even further. The standard stuff sack has a pack size of 25cm x 21cm x 17cm.

This is a sleeping bag designed for minimum weight and maximum warmth but with no compromise on comfort. It’s great to have a sleeping bag like the Firelite that you can rely on when temperatures dip. It’s not the cheapest sleeping bag but it’s certainly one of the best.