This stainless steel digital fractional caliper measures ID and OD from 0–152mm (0–6") with .025mm accuracy; it provides readings in inches and millimeters and gives you results in decimals or fractions, as needed. The caliper has a resolution of .0005" (.01mm), and has a zero set button, making easy work of relative measurements. It's powered by one 1.5-volt button cell battery (SR44, included; replacement batteries are available separately). A protective storage case is included.