The Valandre Mirage has a more narrow cut and substantially more down than the Summerlite, which should in theory make it a much warmer bag….yet the EN comfort is set at 39.2F. I believe they are advertised as a 30F bag (the EN Limit of Comfort) which I tend to agree with having used one at these temperatures regularly throughout the shoulder seasons.
valandre actually post up a -17C rating for the mirage in big bold letters on their page … they even brag about using it to -10C, which normal people would probably be pretty cold at
Made on the principles of the Shocking Blue and the La Fayette, the Mirage will set the standards in its range. This time the benchmark is 26.3 oz (773 g) total, a pack size of only 4.8 liters, and an extreme temperature rating at 1.4°F (-17°C).
Field testers have taken the super light Mirage to 14°F (-10°C) wearing a base layer of underwear and a fleece vest. Even if these are not recommended temperature ratings (metabolism etc. should be considered), field tests have certainly underlined the extraordinary performance of the Mirage.
its up to the buyer on their side to read the fine print and understand EN-ratings

http://www.valandre.com/eng/Sleeping_Bags_and_Outerwear/sleeping_bags/mirage.html
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