The Scubapro Superflow 100cm Hose is a yellow 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. 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 here) and the female end is the universal 9/16” that fit all second stages without a swivel or special connection. The female end is fitted with a high torque nut that requires a special tool to tighten properly. 100CM 1.0m is a good length for an octo hose, hence the yellow colour, so you have enough slack to donate to a diver face-to-face but not too much slack that the hose becomes a hazard. 100cm is also a good length for a drysuit hose from a single cylinder. All you need is a connector to turn this into a QD LPI Hose. Longer hoses are usually prefered for an alternate hose so you can donate to a diver and have some space to move. For a single cylinder primary donate most divers use a 150cm hose for twins on a similar DIR setup 210cm is prefered.