Ultrasonic motor drive
There are two types of USMs, the ring-type USM and the micromotor USM. Ring-type USM is always preferred because of its superior performance and efficiency, and it allows for full-time manual focus operations without switching out of AF mode. Micromotor USM is used in cheaper lenses to bring down the overall cost of the lens. It is possible to implement full-time manual focus even with micromotor USM; however, this is a somewhat inelegant solution, as it requires additional mechanical components, and so has not been widely implemented.

Some USM lenses are identified with a gold ring and the label "Ultrasonic" printed in gold on the lens barrel. All L lenses which have USM do not have the gold ring, but the red ring which denotes them as an L lens. However, they have the label "Ultrasonic" printed in red on the lens barrel.