Digital Calipers provide accurate inside, outside, or depth measurements with selectable units in inches or millimeters from 0 to 12in (0 to 300mm). The TSA-268 and TSA-270 models have an extended length range for precise dimensional checks of most asphalt, concrete, and soil specimens up to 6x12in (152x305mm) Dia.xL. All models have a resolution of 0.0005in (0.01mm). Calipers are constructed with quality stainless steel suitable for rugged use. Features include an easy-to-read LCD display with an On/Off switch, ABS (absolute) and INC (incremental) measurement functions, and a zero calibration button. They also have a smooth-moving head using the thumb slider, locking knob, and easy to open battery compartment for the replacement of the included battery. Includes a protective carrying case. TSA-271 Digital Caliper can measure up to 6in (150mm). The jaw depth is 1.5in (38mm). TSA-268 Digital Caliper can measure up to 12in (300mm). The jaw depth is 2.5in (63.5mm). TSA-270 Digital Caliper can measure up to 12in (300mm). The jaw depth is 3.5in (89mm). Optional TSA-292 Caliper Accessory Kit attaches easily to TSA-271 and TSA-268 caliper models for the measurement of drilled concrete cores to meet ASTM C1542 test standard. Features: Stainless steel caliper with locking knob Convenient On/Off switch conserves battery life Included Items: Digital Caliper with 0-6in or 0-12in Range Battery Protective Carrying Case Accessories: TSA-292 Caliper Accessory Kit fits TSA-271 and TSA-268 Digital Calipers to meet ASTM C1542 requirements Related blogs: Non-Destructive Testing of Concrete: An Equipment Guide Concrete Cracking: Evaluating Width, Depth & Movement