Zafu

A zafu is a round, firmly stuffed cushion, traditionally filled with buckwheat hulls or kapok, used to raise the hips a few inches off the floor for seated meditation. Lifting the hips above the knees lets the pelvis tilt slightly forward, which makes an upright spine far easier to hold without the lower back rounding or the legs going numb.

It is usually paired with a flat mat called a zabuton underneath to cushion the ankles and shins on a hard floor. Buckwheat-filled zafus can be adjusted by adding or removing hulls to change the height and firmness, while kapok fills stay softer and more consistent over time but cannot be adjusted the same way.

The common confusion is choosing a soft cushion instead, which compresses flat under sitting weight and stops providing the height and tilt a zafu is built for. A cushion that flattens out within a few minutes will not solve the hip and knee discomfort that makes floor sitting hard in the first place.