Traceable® Calipers make length/diameter measurements three ways‚Äîoutside, inside, and depth. Digital display models measure to 8-inches (200mm). At the touch of a button units switch from inches to millimeters. Zero button instantly sets unit to zero when jaws are at any position. This permits, without calculations, setting a Floating Zero™ or reference point to read "greater than or less than results with a minus sign displayed". Ergonomic design precision calipers are ideal for measuring the outside diameter of stoppers, the inside diameter of tubing, and the depth of vials. Depth bar extends from the end of caliper. Fine adjustment thumb roller improves reading speeds and position-holding lock screw sets length. Easy-to-read jumbo digital display is 1/3-inch-high. No lubrication is ever required on the ultra-smooth slide bar. Runs on the supplied battery for 10,000 hours. Made of durable acid resistant, hardened stainless-steel or strong, composite carbon fiber. To assure accuracy an individually serial-numbered Traceable® Certificate is provided from the manufacturer's ISO 17025 calibration laboratory accredited by A2LA. It indicates traceability to standards provided by NIST (National Institute of Standards and Technology). Replacement battery Cat. No. CON1039.