generally underlying corresponding front rear and side edges of the top surface in the preferred embodiment side sections 22 and 24 slope slightly upwardly from middle section 26 in such a way as to form a very flattened generally u shape middle section 26 comprising the base of the u while side sections 22 and 24 form the legs of the u thus tri planar construction enables the cushion to conform generally to the sling shape of the seat regardless of the particular curvature and dimensions of the parabola formed by the sling seat lines 44 and 45 extend generally transverse to the side supports of the sling seat 12 and further are believed to act to prevent side to side sliding of the cushion in the sling seat it will be readily appreciated that the bottom of the cushion could be formed by a plurality of generally planar sections comprising two three four or more planar sections however the tri planar construction here described is preferred because it conforms satisfactorily to a wide range of sling shaped seats and yet is simple and economical to manufacture in the particular embodiment here described front surface or panel 28 of cushion 10 is generally in the form of a six sided polygon approximately four inches high at the center of the cushion between top edge 40 and bottom edge 46 while the back of the cushion at 30.