Vernier calipers measure internal and external dimensions with precision, using a fine adjustment thumb roller and reading scales with no parallax.Parallel jaws are 40 mm (1.5") deep; inside jaws and round plastic rod depth gauge add valueUpper scale: 150 mm with 0.1 mm subdivisions; lower scale: 6 inches with 0.005" subdivisionsMolded in rigid plastic; will not scratch like metalNon-conducting, corrosion resistant, and lightweightNote: Units are not serialized, so no calibration documentation is available.