What works
- Genuinely warm at Gorak Shep with a liner
- 640 g and packs to 3 litres
- 850+ fill power down
What does not
- Very expensive
- Narrow cut restricts side sleepers
- Not warm enough for camping treks in winter
Rating versus reality
Manufacturer comfort ratings are laboratory figures and assume a mat, a base layer and a person who sleeps warm. The SpIII's −9 °C comfort rating held up in a Gorak Shep lodge at roughly −12 °C outside — with a merino liner, a hat and a hot water bottle. Without the liner it was marginal.
About the author
Tom Eriksen
Gear editor & photographer
Tom tests trekking equipment the only way that produces honest answers: by carrying it for weeks at a time above 4,000 metres. He shoots most of the photography on this site and writes the gear reviews, comparison tables and packing lists.
Writes about: Trekking gear · Photography · Packing and weight