for attaching the lens hood. The hood mount is of a bayonet style on most EF lenses, though a clip-on style hood mount is used for a small selection of current lenses. Tripod collar: This feature is found on most longer focal length lenses, and macro lenses. The tripod collar is used for attaching the tripod ring. There are two main styles of tripod rings. One type is opened up, placed on the lens' tripod collar, then closed and tightened. The other type does not open, but instead is slid up the lens from the mount end (which can only be done when the lens is not mounted on a camera body) and tightened. To set the tripod ring so that it is level with the lens, rotate the ring until the index mark on the tripod ring matches the index mark on the distance scale. The tripod ring is used for attaching a tripod/monopod near to the point of balance of the lens-body combination, more conveniently than the camera body. In the case of larger and heavier lenses, there is also less strain on the lens mount if the body is supported by the tripod-mounted lens than if the lens were to be supported by a tripod-mounted body. Related technologies Ultrasonic motor drive Ultrasonic motor (USM) lenses appeared with the introduction of the EF 300 mm 2.8L USM lens in 1987. Canon was the first camera maker to successfully commercialise the USM technology. EF lenses equipped with USM drives have fast, silent and precise autofocus operations, and consume less power compared to other AF drive motors. There are three types of USMs: ring-type USM, micromotor USM, and Nano USM. Ring-type USM allows for full-time manual focus (FT-M) operations without switching out of AF mode. Micromotor USM is used to bring down the cost of the lens. It is possible to implement FT-M even with micromotor USM; however, it requires additional mechanical components, and the vast majority of micro-USM lenses do not offer such capability. Nano USM was introduced in 2016 with the release of Canon's latest iteration of the EF-S 18–135mm lens. It is intended to offer the AF speed of ring-type USM with the quietness of STM mechanisms (see below). Some older USM lenses are identified with a gold ring and the word "Ultrasonic" printed in gold on the lens barrel. L lenses with USM don't have the