Abstract: A precision caliper gage to measure an internal or external dimension of a body. The caliper gage provides for quick and easy attachment of measuring components and for automatic interplanar alignment of measuring components as they are attached to the gage. A mainframe has a portion parallel to a longitudinal plane and is adapted for attachment of a pivot member in alignment with the longitudinal plane. A first measuring arm is mountable on the pivot also in alignment with the longitudinal plane. A second measuring arm is mountable on the mainframe in alignment with the longitudinal plane and cooperates with the first arm to measure a dimension. A measurement indicator is mountable on the mainframe with a measurement-responsive indicator stem in alignment with the longitudinal plane and responsive to measuring movement of the first measuring arm.