Abstract: A reversible seat supplement, or seat cushion and/or backrest, includes upper and lower portions which are both contoured, generally concave on one side and convex on the other side; and a keyhole shaped opening including an enlarged opening toward the rear at the base of the spine and the coccyx, and a narrow slot for the anal and urogenital triangle region extending forward to a point more than half way across the seat. Wedge shaped openings angling forward and outward from the central portion of the seat avoid pressure on the sciatic nerves. An optional front vertical opening may be provided to receive a container for a cup of coffee or the like. Bulky material from the seat or the backrest prevent the backrest from flopping forward onto the seat, thus limiting normal folding of the seat back to about 90 degrees from the horizontal seat/pad. The seat back has optional devices to adjust the lumbar pressure.