Ports for DSLR housings are an essential part of the underwater photography system. Getting the right port for the job is an important step for making sure that you get the best possible image quality from your underwater camera. The Nauticam DSLR ports have 120mm port opening diameter and come with either acrylic or glass (dome) lens elements. Extension rings are used to add length to the port so that the internal lens sits at the right position inside the housing. Don't forget that you will also need to get a zoom gear if you want to use the lenses' zoom and a focus gear if you want to do manual focus/focus pulling.