N120 Extension Ring 55 ~with LockThe Nauticam Extension Ring 55 with Lock is part of the N120 Port System and can be used to add 55mm effective length to an N120 Port setup. See Port Chart for more details on choosing the correct extension and port. Technical Specifications Depth Rating 150m Port System N120 Weight 0. 29kg Port Opening Diameter 109mm from SN A055057 and later Port Diameter Body Material Anodized Aluminum Alloy Port Material Port Coating Port Shade Material Removable