Small size (BBP-2072-M) is designed for inserts that will cover the lower part of driver's body, including hips, pelvis, thighs and lower back. Your seat needs to have rib foam installed when using a small-size insert. Use Medium or Large size for full-body seat inserts, which should extend up the driver's back and end at shoulder belt holes. In most cases, no rib foam is needed on seats with full-body insert pours.