Not just "D" but "Super D" - the Flylow Super D Mittens throw down with super durability, super warmth, and the kind of coverage you need on that super pow day when the weather is simply nuking. Re-designed with supple but burly Goatskin leather and insulated with recycled Greenloft™ insulation, the Super D Mittens offer the best hand-warmth bang for the buck anywhere.