Wonderful wool keeps this pillow working very hard at keeping you comfortable. Wool is a wonderful natural material & it's the ideal fill for peaceful slumbers all year long. We use Australian Michell wool for its reliably excellent quality & sustainable fill. Naturally temperature regulating; wool allows your body to breathe so you won't wake up feeling clammy. It's naturally hypoallergenic & so is ideal for allergy sufferers & children. This medium firmness pillow has a dense, supportive feel & is ideal for back-sleepers. Side-sleepers may want to add in an extra pillow to increase pillow height.