The natural insulative properties of sheepskin gives thermostatic properties to the boots: the thick fleecy fibers on the inner part of the boots wick moisture and allow air to circulate, keeping the feet at body temperature.This property allows Ugg boots to keep feet warm in cold weather and cool in hot weather.

The original design was a pull-on boot in natural (undyed) tan sheepskin, about 10 inches (25 cm) in height, with rounded, almost shapeless uppers; this is now described as the “classic” design. Produced by a number of manufacturers, they come in a variety of colours, including black, pink, blue, chestnut, and fuchsia.They are available in both pull-on and lace-up varieties and their height can range from just above the ankle to above the knee.

 Some variations of ugg style boots have also been made from kangaroo fur and leather. There are also synthetic boots. Although derided as “fake” by some in the industry,their lower price made them appealing to large retail chains such as Myer.

In 2009 American podiatrist Ed Chairman raised concern that the regular wearing of ugg boots could be deleterious to foot health due to the lack of arch support.