The waterproof features protect the buckwheat hulls which can easily be damaged when exposed to liquid. There are numerous causes, including accidental drinks spilling, pets may urinate on it, or using the cushion outdoors in high-risk areas such as the beach, lake or in the rain. When the buckwheat hulls are slightly moist, this increases the risk of mildew growing inside the cushion. In addition, the cover also has anti-UV features which help extend the longevity of the buckwheat hulls as well as the cushion fabric from long sun exposures.