Because the lumbar cushion is pre-shaped, it gives the right support to the lower back while sitting. You can also use a lumbar cushion to improve your sitting posture. To provide the right support for your lower back, the cushion must be firm. That is why the VITILITY lumbar cushion is made of PU. PU is a durable hard plastic. As a result, the lumbar cushion always retains its shape and always offers the right support.