• V-1 Calibration Block  V-1 Calibration Block  The V-1 Calibration Block is used for calibrating ultrasonic flaw detection equipment in both laboratory and on-site conditions. It includes a 100mm radius, 1.5mm and 50.0mm holes, engraved reference mark scales, and slots at the zero point which provide calibrating signals at intervals of 100mm range. In accordance with British standard BS 2704 Block A2 Mod. 1,  DIN 54-120, and ISO 2400.