If you want to upgrade to 800-fill power goose down for the same 0°C range while bringing the weight under the one-kilo mark, the Aegismax M3 is the logical step.
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The field guide helps you choose based on skill level, temperature, needs, and weight. Support answers specific questions.
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The Aegismax D2 has a comfort temperature of 0°C and a lower limit temperature of -5°C, measured to the EN 13537 standard. These values apply under standard conditions: sleeper in thermal base layers, on an insulated sleeping mat. It is designed for hiking, bivouacking use (3 seasons).
The Aegismax D2 is filled with 650 fill power, RDS certified. The Aegismax D2 weighs 1006 g, which places it in the lightweight 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.