This Ikelite Locking Device works with the 5510.10 Superwide Port Body for housings with the 2-lock Port System. It is also compatible with the 5510.11 Superwide Port Body for housings with the 4-lock Port System. The "L"-shaped safety device limits the port's angle of rotation and attaches and detaches with a thumbscrew for quick and easy port changes. This Locking Device will prevent unintentional detachment of the 8" port and port body from the housing.