This drawing shows you the key measurement points. When making your measurements, use a straight edge, not a tape measure. A tape measure will conform to your bodys shape giving a false measurement. A straight edge (yardstick) will show the width of your body as it would be in the seat. Starting with the chest width (A), this measurement should be taken 1-1/2 inches below the armpit. Next, the shoulder height (B) is taken by sitting on a flat surface with your legs hanging over the side. Place the straight edge on the flat surface and measure up to the top of your shoulders. The armpit height (C) is measured the same way as the shoulder height, except you measure up to the armpit. For hip width (D), using the straight edge, measure across the midsection of your hip while sitting on a flat surface. This gives a true hip-width measurement as if you were in the driving seat. The last measurement is chest depth (E). This is done by placing your back flat against a wall and measuring 1-1/2 inches below the armpit from the wall outward.