Fatigue cracks often develop on the inner surface of annular components such as collars. In some instances, these cracks have been identified as the cause of catastrophic failures. Traditional ultrasonic inspection of such parts can be difficult and time- consuming. Instead, circumferential waves guided in the annular structure interrogate at once the entire path between the source and the receiver thus enabling for fast inspection of relatively inaccessible regions. However, the modal complexity of the ultrasonic signals is a challenge which must be addressed before practical implementation of the technique. Specifically, it is important to control and select the desired modes of propagation in the waveguide [1–4].The approach taken in this paper is analytical, numerical and experimental.