This caliper is based on a special design, enabling convenient measurements of the distance between a patient's back and the front of his abdomen to be taken. It was developed to aid the prediction of cardiac risk by measuring sagittal abdominal diameter in supine subjects. A clear, easy to read graduated strip is fitted into a recessed slot in the main alloy column. A built-in spirit level is provided to help ensure that the caliper is vertical when the reading is made.