It is important that your seat fits you perfectly if it is to keep you safe and provide the intended level of support. The height, width, and depth of the seat are important, as are your measures that relate to these areas. This means that you need to measure your width at your shoulders, waist, and hips, to ensure the right lateral fit. You should also measure the length of your upper leg when sitting; you need the measurement from the underside of your knee joint to the rear of your bottom. This ensures that you can fit comfortably in the base of the seat and that any padding is in the right places. If the seat is not deep enough for your measurements, your balance will be wrong, and the seat will not hold you correctly. If the length of the top of your legs is too short for the base of the seat, then this might impair your driving ability. The height of your upper body is important. You should take a measurement up to your shoulders, another to the base of your neck, and a third to the top of your head. This ensures that the seat is tall enough and that neck and shoulder support is in the correct place.