ARRI PL MOUNT
The Arri PL (Positive Lock) mount is the most common adapter type for cine lenses. The mount contains four pronged flanges that each contain a notch towards the center. Any of these four notches can be used to align the mount to a locating pin located approximately 45 degrees clockwise from the top of the camera’s lens mount. This means that the lens can be oriented in any of four different configurations, which may be decided by factors such as [focus puller](https://en.wikipedia.org/wiki/Focus_puller) position, camera position, and preference to working with meters or feet (if a lens has different line indicators on each side).
The mount is locked into place using a friction locking ring that, in conjunction with the four prongs of the flange, creates a very strong lens seating. This has become a crucial factor in recent years, as bigger lenses with zoom capabilities, longer focal lengths, or larger lens elements have increased the need for mount stability due to the greater stress placed upon the mount by these devices.
Flange focal distance: 52.00 mm
Diameter: 54.00 mm