Depending on the test results, the piston is then classified into one of two groups, ACCEPTor REJECT. The computer acquires the number of pistons which have been tested, separated into ACCEPT and REJECT, and, if required, produces a displayed report. The circumference of the piston with a display of the flaw areas can be printed. After the ultrasonic test, which takes approximately 8 seconds per piston, sorting is made and the piston is transported further.