ASTM E428 Area Amplitude Calibration Blocks Set of eight flat-bottom hole blocks used to determine the relationship between flaw size and echo amplitude by comparing signal responses. Metal travel distance is 3.000” for all blocks, and FBH diameter ranges from #1 (1/64") to #8 (8/64"). In accordance with E428. Includes our NIST traceable dimensional certification report, ultrasonic inspection report and response plot from Tactic Inc, and the certified material test report