Maternity SI-LOC, developed by IAOM, is tapered and wider at the innominates so pressure is distributed more evenly. The Maternity SI-LOC is not bulky under garments and the breathable fabric adds comfort. Wide, medical grade non-slip pads ensure that the Maternity SI-LOC stays in place. Includes a special, detachable abdominal support pad. The small/medium size fits up to 36 in ASIS to ASIS. The large/extra-large size fits up to 36 in to 45 in ASIS to ASIS. Measure the distance from ASIS - dorsally around the back - to the other ASIS. Not returnable.