I ordered this from Amazon last year. I used it on Mt. Kitadake in January, where the temperature was below -20°C, and I slept for 8 hours without being woken up by the cold. My clothing consisted of thick wool on top and thick tights on the bottom. I am selling it because I no longer plan to do tent camping in the severe winter alpine zone. The following is quoted from the official website: This model has high heat retention and can be used in the winter in Japanese mountains at altitudes of 2000m to 3000m. The fabric uses water-repellent, lightweight, and durable 20D polyester ripstop. The insulation material is 900g of high-quality 750FP white duck down. The box construction, which maximizes the loft of the down, provides high heat retention. The zipper uses a 170cm YKK coil zipper that can be opened and closed from the foot, making temperature adjustment easy. It is equipped with a zipper-jamming reduction part. In addition, a large storage bag is standard equipment, which is ideal for long-term storage.