There's some detail on the interior of the sub on their site [1]; note the slider on the "Key Features" photograph that shows you the inside when the slider is

There's some detail on the interior of the sub on their site [1]; note the slider on the "Key Features" photograph that shows you the inside when the slider is moved to the left. [1] https://fivedeeps.com/home/technology/sub/ https://fivedeeps.com/home/technology/sub/