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.
I like the feeling of a little more security on my port housing under water.
I am giving this product 3 stars because the instructions were very unclear, thus forcing me to skip using the product with my 15mm fisheye and going with my 14mm port that does not require the lock. It also does not bring a small allen key that is necessary to follow the instructions. Didn't have one with me on a cruise ship, so I did not get to use it. Got home from my vacation, got the allen key and put it together. Seems to work as described but haven't taken it in the water yet.