7/16’’ Port Plug -Aqualung This is our Aqualung Port Plug. The finish on this version is a little nicer than the generic. They use the standard 5/32 or 4mm allen key. The port plug comes with a viton oring. Ok, I am going to blow your mind here. A port plug is a port plug. You do not need to buy an expensive port plug for your fancy reg. Any port plug will do. So maybe I did not blow your mind but hopefully I kept someone from paying way to much money for a port plug just so they can have one specifically for there reg. There are three different sizes of port plugs; 3/8’’ Port Plug – otherwise know as the low pressure port plug. This is the plug used on the low pressure side of the regulator. The low pressure side is where your second stages plug into and your bc inflator hoses. 7/16’’ Port Plug – otherwise know as the high pressure port plug. This is the plug used on the high pressure gauges. 1/2’’ Port Plug – this is the common big one used on the old Apeks, Mares and Dacor regulators. There is usually only one port this size on the regulator.