Dimensions: 23.8 x 7.7 cm Measuring range: 150mm Number of batteries: 1 X LR44 - (Included) Precision tool that allows you to measure the diameter of pearls, cabochons, pendants, rolled stones, etc.It gives the exact interior and exterior measurements, on its digital screen but also the thickness of the parts. The caliper gives you precise measurements up to 15 cm.A unit button allows you to switch from mm to inch. Instructions for use : Before using the caliper, press the red button to turn it on. Then choose the appropriate jaw and unit of measurement (millimeters or inches). Start measuring. The device has a reset function to ensure optimum accuracy.