Strategically placed flared openings to lighten and strengthen seat. TIG welded .100" 5052 grade aluminum. MIG welded inside for added strength. Offset aluminum extrusion around perimeter of seat for added rigidity. Progressive rib bead adds extra strength. Upholstery is double stitched around belt openings and all stress points. Multi-position lap belt openings for easy mounting. Submarine belt opening is standard. Machine plate added to reinforce shoulder belt openings. Seat back is double cross broke for added strength and comfort. High density foam on rib supports for added comfort.