To All those who suffered with back pain just like me because of the Prius car seat or any car to that matter , I found a solution for this and I have no pain anymore. I bought a wedge seat with back and lumbar support and it is really helping and I have no traces of pain anymore. Pasting the site and seat cushion that I bought and tried for more than a month before posting here, hope this helps you as it did for me...Good luck!