Ugg boots (sometimes called uggs) are known in Australia and New Zealand as a unisex style of sheepskin boot. It is typically made of twin-faced sheepskin with fleece on the inside, a tanned outer surface and a synthetic sole. Ugg boots originated from Australia, initially as utilitarian footwear worn for warmth. They were often worn by surfers during the 1960s. In the 1970s, the boots were introduced to the surf culture of the United Kingdom and the United States by local surfers returning from surfing competitions in Australia.