A sleeping bag designed to keep you insulated from the elements and with added features it perfroms above and beyond.EXOTHERM Extreme Fill - a high quality hollow fibre that has had its surface area increased dramatically by two processes; firstly the fibres are crimped so they have a powerful lofting ability, secondly the fibres are twisted together in pairs offering even more surface area to trap warm air. The result is a high loft fill that captures a large volume of warm air and restricts its movement offering remarkable insulation.