The Summit 250 Square Sleeping Bag is perfect for colder camping adventures. With a 3/4 season rating, a comfort rating of -1C to 4C and an extreme temperature of -17C. 100% polyester ripstop, with a square shape for campers who prefer more leg room. You can unzip and attach another bag to create a well insulated double bag. 3/4 Season - Cold nights early Winter Extreme Rating - Can be used for extreme temperature of -15°C. This is a survival temperature only. The bag is not intended for regular use at this temperature Comfort Temperature - The comfort temperature for this sleeping bag is 5°C to 0°C. This is the minimum temperature that the sleeping bag is designed for Insulation - Insulated with hollow fibre stuffing Envelope Shape - Envelope shaped bags are essentially rectangular,.