A device that calibrates phase-measuring interferometers has been released by Engineering Synthesis Design Inc. The CaliBallT — a 25.4-mm-diameter silicon nitride ball and kinematics mount — determines errors in the transmission-sphere reference surface. Calibrations can be done in as little as 10 min. It works with any brand or make of transmission sphere and can be used to qualify those with f numbers ranging from f /0.7 to f /11 or beyond. The device measures 42 × 51 × 56 mm and weighs 287 g.