Pipeline wall measurement with liquid-coupled, ultrasonic in-line inspection technology is well established after more than 25 years of industry use. However, where pitting and pinholes are concerned, reliable detection and accurate sizing were particularly challenging for these technologies until the limiting factors regarding sensor density, processing speed, and axial scan pitch could be overcome with recent PII innovations. When assessing a defect’s severity for integrity studies and fitness-for-purpose investigations, a key consideration is the accuracy of the reported dimensions — the probability of detection (POD), and the tool’s sizing accuracy, which is stated as an accuracy level and a percent certainty. Magnetic flux leakage (MFL) and ultrasonic technology (UT) are well proven for the detection of metal loss and corrosion. We set out to build a new UT tool that would beat these specifications, and increase the visibility of pitting and pinhole corrosion sites.