Complex sentence: The mechanism of the regulator is packaged in a usually circular metal housing mounted on the cylinder valve behind the diver's neck, and the air flows through a pair of corrugated rubber hoses to and from the mouthpiece.
Split into simpler sentences: The mechanism of the twin hose regulator is packaged in a usually circular metal housing mounted on the cylinder valve behind the diver's neck. The air flows through a pair of corrugated rubber hoses to and from the mouthpiece.