A zafu is a round cushion also known as the Zen cushion used in meditation in Japan. You can place it over your mat or a zabuton during your practice. It is filled with buckwheat hull and the cushion cover on the Zafu is 100% cotton. A Zafu placed under the hips lifts your upper body slightly and helps you to effortlessly straighten your spine.It is good to sit on a Zafu if your work involves sitting for long hours.