The most effective way of ultrasonic defect sizing currently recognized is the tip echo method, and it has broad and practical applications. Tip waves have very weak intensity, about 20 dB lower than the mean echo, and this prevents their use in many instances. Recently, low noise full digital flaw detectors have been developed, which make it very easy to catch tip waves. In the reflection by a small crack, we are now able to catch several tip waves easily in one shot. Moreover, the distances between two tip echoes are more stable for the fluctuation of experimental condition than the conventional method. Thus giving us more information than by the conventional method. Numerical experiments must be used, in order to distinguish each tip echo.