Absolute insulation for high-altitude mountaineering
The Aegismax Ultra is a thermal protection tool intended for demanding expeditions. When facing temperatures of -30°C, maintaining metabolic functions during sleep is the absolute priority. This expedition sleeping bag requires rigorous management of your bivouac environment (ground insulation and dry clothing) so that the exceptional quality of its fill can reach its full heat-retention potential.
3D architecture and maximum heat retention
This model incorporates three-dimensional sidewalls and continuous wraparound baffles, a design that maximizes the expansion of the RDS-certified 950-fill-power goose down while eliminating dead compression zones. The adjustable thermal collar literally seals the interior. The use of an ultra-thin yet extremely durable 10D nylon allows for optimal breathability, helping to limit moisture buildup before it freezes in the insulation.
Certified materials, performances verified by an independent laboratory
The filling has been tested according to the IDFB Part 10-B 2023 standard by the IDFL (International Down and Feather Laboratory), the world's leading body for down product certification. The measured Fill Power reaches 960 in³/30g, above the stated nominal value of 950 cuin (IDFL report #25-891483). This document is available upon request for this extreme cold expedition sleeping bag.
Material certification and traceability
The IFLEX® fabric has undergone physical performance testing according to the EN 1103 standard (all criteria passed, report #26-971031) as well as a full chemical compliance analysis according to the REACH EC 1907/2006 regulation (result fully compliant, report #26-971032). This level of traceability is rare in the expedition sleeping bag category and provides a concrete guarantee for the mountaineer committing their safety in environments where there is no easy return when using this extreme cold weather down sleeping bag.
At the opposite end of this extreme spectrum, if the winter season is over and you are looking for a minimalist down sleeping bag under 450 grams for purely summer nights (around 11°C), the ultra-compact Aegismax Air model will radically lighten your load.
Why pay more for the same performance?
The Aegismax Ultra was compared with the Cumulus Excuistic 1200. The finding is simple: you get equivalent technical features and warmth without paying the brand premium. Keep your budget for your next expedition.
Data checked against the brands' official product pages — subject to change.
Doubt about which bag is right for you?
The field guide helps you choose based on skill level, temperature, needs, and weight. Support answers specific questions.
Find my bag Contact supportFrequently Asked Questions
The Aegismax Ultra has a comfort temperature of -30°C and a lower limit temperature of -38°C, measured to the ISO 23537 standard. These values apply under standard conditions: sleeper in thermal base layers, on an insulated sleeping mat. It is designed for mountaineering, winter expeditions, extreme cold bivouac use (4 seasons / Extreme cold).
The Aegismax Ultra is filled with 950 fill power, RDS certified. The Aegismax Ultra weighs 1534 g, which places it in the standard category.
A down sleeping bag is insulated with goose or duck down and feathers, whereas a synthetic bag uses polyester fibres. Down offers a better warmth-to-weight ratio and packs smaller than synthetic insulation of equivalent warmth; synthetic keeps more of its insulation when damp.
A well-maintained down sleeping bag retains 80 to 90% of its insulating properties after 5 to 10 years of regular use. The main cause of degradation is long-term compressed storage, which gradually breaks the down clusters. Washing once a year with a down-specific detergent and storing the bag uncompressed out of season significantly extend the life of the fill.
The ideal comfort rating depends on intended use. For summer trekking in France (Alps, Pyrenees, GR20), a comfort temperature between 0°C and +3°C covers almost all situations. For static summer camping in the lowlands, +5°C to +10°C is enough. For extreme cold or winter wild camping in the mountains, aim for -10°C comfort minimum. The comfort temperature is always measured to EN 13537 / ISO 23537-1 / GB/T 38426.