The patented Outex sealing is simple, and applies to all of the optical products we make; front and rear glass ports, domes, tripod adaptor, cable adaptor, etc.
There are videos and images on the Questions, Installation, and How It Works pages as well as our YouTube channel.
The image shows the 3 parts on all of our sealing products. Every product has a proprietary washer and a nut that threads the washer in between. These products work in conjunction with our cover's built-in o-ring lips. The cover lips align against the base of the inner component (right size of the image above). Think of the washer as the "female" match to the cover's lip "male". The washer rests on the cover's lip, which is lined up evenly around the base of the inner part. The threaded nut then threads onto the inner part, squeezing the washer and cover lip together, tighter and tighter as it turns/tightens.
This system gives you both visual and tactile feedback so you can not only see it working, but also "feel it" working. The watertight seal increases as the pressure you apply to the thread increases, so the user can control it. You can barely tighten it for casual use, or seal it tight for more intense use, such as a surf photo session in the water, for example.