The Slumberdown Wonderful Wool Duvet is filled with 100% British wool. Wool fibers act like a spring, meaning they can continuously resist pressure and flattening and still bounce back, which makes wool a perfect filling for duvets. Wool fiber is incredibly complex and made up of lots of different layers, which create pockets that trap air and help to circulate heat, enhancing insulation and warmth. It absorbs the sweat we produce during the night and then releases it when the atmosphere is dry, keeping skin dry and comfortable. As well as this, wool breathes naturally and constantly adjusts to external conditions, which helps to regulate temperature and ensure comfort. All these characteristics make this wonderful wool duvet from Slumberdown a great choice for all seasons. To enhance the effects of this impressive filling, the Wonderful Wool duvet has a 100% cotton cover. Also naturally breathable, the cotton ensures that the benefits of the wool filling are not lost, working harmoniously together to deliver an optimum sleep environment for you all year round.