The Scubapro Black Rubber Superflow 56cm 22 inch Hose is a high airflow hose for your regulator with a large, smooth internal bore so it won't restrict air flow.  The rubber outer shell both protects the inner hose and adds some weight to the hose so they don't float in the water.

The 56cm hose is perfect as a back up hose that sits around your neck, with the second stage held in place by some shock cord as a neckless.

3/8" male thread will fit most regulator 1st stages today (except some Mares and older Apeks that use a 1/2" thread but you can read more about thread sizes and the female end is the universal 9/16€ that fit all second stages without a swivel or special connection.

Low Pressure (LP) Hose is a made from Traditional Rubber material. Hose has Corrosion Resistant Chrome Plated Brass Fittings with a Standard 3/8" Male threaded End for attachment to your First Stage Regulators LP Port.