Ultralight 800FP down sleeping bag for 3-season trekking and bivouac
The sleeping bag Aegismax Windhard Dusk II combines an RDS-certified 800FP Ultra Dry grey duck down fill with a DWR-treated 7D Nylon Ripstop iFlex fabric, for a weight of 651 g in the Regular version, compression sack included. The comfort temperature is set at 1°C and the limit temperature at -4°C, measured according to the EN 13537 standard in standardized laboratory conditions, with an insulating pad, long underwear, and in a dry environment. In real-world field conditions, particularly at altitude or with residual humidity, plan for a 3 to 5°C margin on the displayed limit value.
Ultra Dry treatment and thermal leakage prevention structure
The Ultra Dry water-repellent treatment applied to the down preserves some of its loft in the event of light moisture, perspiration, or nighttime condensation, though it does not replace a waterproof bivy sack when bivouacking in exposed conditions. The wraparound structure features a draft tube, a draft collar at the neck, and an anti-snag system on the zipper: three design elements that reduce heat loss in the areas where it typically occurs on this type of product.
Baffled lining structure: even distribution of insulation
The Dusk II features a baffled lining structure that keeps the down in place throughout the night. Without this construction, the fill would migrate downward due to body weight and heat, creating cold spots around the shoulders and sides. With 436 g of 800FP down distributed in compartments, the insulation remains consistent from head to toe: this is the principle that allows it to reach a 1°C comfort rating at 651 g, without increasing the amount of fill.
If you prefer to remove the back section to lighten it to 509 g for the same thermal range, the Aegismax Wind Hard Twilight quilt trek is the open version to consider.
Why pay more for the same performance?
The Aegismax Dusk II was compared with the Valandré Swing Co 450. 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.
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Find my bag Contact supportFrequently Asked Questions
The Aegismax Dusk II has a comfort temperature of 1°C and a lower limit temperature of -4°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 Trekking, bivouac use (3 seasons).
The Aegismax Dusk II is filled with 800, RDS certified. The Aegismax Dusk II weighs 651 g, which places it in the ultralight category.
The lower limit temperature is the lowest temperature at which a reference man can maintain his body heat curled up, according to EN 13537 / ISO 23537-1. It does not correspond to comfortable use: below the limit temperature, the sleeper is likely to suffer from the cold. For real use, the comfort temperature is the main reference.
The minimum recommended temperature is the bag's comfort temperature, measured to EN 13537 / ISO 23537-1. For a 0°C bag, this means a standard sleeper can spend a night without feeling cold at 0°C, provided they use an insulated sleeping mat (minimum R-value of 2 to 3) and wear thermal base layers.
For extreme cold (below -10°C), the most suitable bags combine high-loft down (700 cuin minimum, ideally 800 cuin and above) with a mummy cut that limits heat loss. A sleeping mat with an R-value of at least 4 is essential alongside. For nights between 0°C and -5°C, a good-quality 3-season bag with a 0°C comfort rating is generally sufficient.