The Fernos Max Insulated Jacket is a synthetic insulated jacket built to work as a standalone outer layer through sustained cold. Its PeakFill(R) Active Mapped Insulation runs at nearly double the weight of a standard midlayer fill, holding warmth through long stretches outside rather than short bursts of effort. Zippered underarm vents let heat escape the moment activity picks up, and a Relaxed Fit with a fixed hood leaves room to layer underneath without feeling bulky. What Our Gearhead(R) Experts Are Saying:"I wore this alone through a two-hour outdoor shift in single digits and never reached for another layer. When I finally started moving fast enough to sweat, unzipping the underarm vents brought the temperature down in seconds."