These are octo hoses for scuba diving. They are suitable for use with all breathing gases including air, nitrox, trimix and oxygen, and have fittings made from quality chrome-plated brass. Length is measured from end to end of the hose, including the fittings and their threads. The typical low pressure regulator hose is a 3/8-inch male at the end that screws into the first stage LP port, and at the other end you'll find a 9/16-inch female that screws onto the second stage regulator body.
