Made of natural buckwheat hulls Recommended for side sleepers. Buckwheat hulls can be inserted and removed from the zipper portion, so you can fine adjust the height. Buckwheat picks are classified as a firm pillow material. Buckwheat hulls can be used for gardening compost. The hot air treatment of approximately 60 degrees Celsius repels moisture and prevents the growth of insects, mites, mold, but insects may be excited if used and stored in a high humidity condition for a long time. It is recommended that you air dry it in the sun for about 30 minutes a week on good weather. In addition, the buckwheat may become crushed and powdered during use. Therefore, it is not recommended for people with allergies or asthma. The black granules from the pillow are powdered buckwheat hulls and are not defects.