White down filling material, comfortable and keep warm. Down is fluffy, sleeping bag is light, but it's warm. Use zipper of international famous brand.Use waterproof fabric, light rain is no problem, of course, it is not recommended to get wet when it rains. Durable shell that will stand up to years rigorous use. Innovative Footbox Design-Footbox is vaulted so you have even more roon for your feet.Added insulation in the bottom of the sleeping bag keeps your feet warm. Down is very soft and light. There is a small gap between down and down, which causes the air convection in the sleeping bag to be bad. It can form a layer of insulation layer which is isolated from the outside, so that the outside cold air is not easy to reach the inside, and the inside hot air is not easy to reach the outside, so that the temperature can be maintained.