Trekking poles (also known as hiking poles, hiking sticks or walking poles) are a common hiking accessory. When in use, they resemble ski poles as they have many features in common, such as baskets at the bottom, rubber-paded handles and wrist straps. Unlike ski poles, however, they are often made in two or three sections and can be extended and retracted as necessary for use. Their maximum length is usually 135 cm (54 inches). Some poles come with spring-loaded tips to aid walking under normal conditions and to reduce wrist strain. Trekking poles are usually made from lightweight aluminum or carbon fiber. When fully retracted, they can easily be stored in the side pocket of a backpack.