Trail’s synthetic sleeping bag lab test gave result of -31 deg C so it is mega-warm and ideal for high altitude peaks; massive zip baffle and shoulder baffle; excellent snag-fee zip; very water-resistant. But 2935g is heavy; confusing labeling gives Hypothermia Risk temperature value of -40 deg C rather than the comfort temp of -11 deg C as it should; very high price tag; too warm for UK winter walkers.