Nauticam Mini extention ring 20The Nauticam N85 Extension Ring 20 can be used to add 20mm effective length to an N85 Port System. See Port Chart for more details on choosing the correct extension and port. Technical Specifications Depth Rating 100m Port System N85 Weight Port Opening Diameter Port Diameter Body Material Anodized Aluminum Alloy Port Material Port Coating Port Shade Material Removable Port Shade Spare O ring 90143