Perfection Evolved. Version 2.0 of our premium ultralight has an improved fit that's more comfortable and mobile, a slightly longer length for added coverage and warmth, a softer fabric to further enhance the comfort, and a secure drawcord hem to seal out cold and fine-tune the fit.As an ultralight insulating layer, the MicroTherm is thinner than traditional down jackets. But that combination of minimal bulk and effective warmth is what makes it special, and is the result of its patented construction and the exceptionally high-loft Premium Down that it holds close to the body for maximum thermal efficiency.