We offer 3 sizes of port plugs...but most regulators only have 2 size plugs on their first stages. Port plugs can be either a high pressure (HP) port plug or a low pressure (LP) port plug. All O-rings on these plugs are oxygen compatible and Nitrox ready. Most LP and HP port plugs use either a 4 mm or 5 mm Hex key for installation and removal.

The most common size port plug for HP ports (SPG, air integrated computers, transmitters) is 7/16-inch. Some early vintage (perhaps better described as 'antique') first stages have the high-pressure port size same as a 3/8-inch low-pressure port, but these are extremely uncommon (and dangerous.)

The most common size port plug for LP ports (BC inflator hoses, Regulator hoses) is 3/8-inch. This size is used on just about every brand of regulator made.

There are a few unique regulators available with one oversized 1/2-inch LP port. This 1/2-inch size is not common and is usually found as an option on some Apeks, Aqualung (US Divers) and Mares brand uncommon first stages. We recommend the Omniswivel brand 1/2-inch LP port plug for use on the rare Apeks DST swivel first stage with both a 1/2-inch port AND with a 5th port upgrade. See also Regulator Hose, Oversized LP (1/2-Inch).