 This means that a single set of standardised safety procedures is not possible while diving with team members using back-mounted tanks.The UTD Z-system provides an approach to emulate back-mounted Hogarthian configuration by quick-connecting two primary gas supply sidemount cylinders to a manifold block mounted behind the shoulders on the Z-system harness, from which long hose primary and necklace secondary demand valves are supplied, reducing the demand valve arrangement to a functional approximation of the standard Hogarthian configuration at the expense of additional complexity of components.The added failure points may not be necessary when using more than one bottle at the time.