Editing Scuba set (section)

===Stage mounting===
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[[Technical diving|Technical divers]] may need to carry several different gas mixtures, or several extra cylinders with additional gas needed for the dive. These are intended to be used for different stages of the planned dive profile, and for safety reasons it is necessary for the diver to be able to check which gas is in use at any given depth and time, and to open and close the supply valves when required, so the gases are generally carried in fully self-contained independent scuba sets, which are suspended from the harness at the diver's sides. This arrangement is known as stage mounting, or sling mounting, the scuba sets known as stage sets or stage cylinders, and usually applies to cylinders additional to the main back mounted set or sets.<ref name="tecline" />

====Drop tanks====
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Stage sets may be cached along a penetration guideline to be retrieved during exit for convenience. These are also called [[Drop tank (scuba)|drop tanks]]. A drop tank is usually rigged to be carried in a sling mount, and has a regulator with a pressure gauge fitted and is deposited at a suitable place along the guideline, usually clipped to the line to ensure that it can be found again. The amount of gas in a drop tank can vary depending on how it is intended to be used. The gas mix must be suitable for the stage in which it will be used, and will be marked on a label, usually with the user's name, to avoid confusion. The cylinder valve is closed until the time of use.<ref name="Davis" />

====Stage-only mounting====
Similar in basic concept to side mount and may be confused with it, but does not use bungees to control the top of the cylinder. No back mounted cylinder is carried, and all cylinders are slung at the sides like regular stage cylinders, so they do not tuck in under the arms for streamlining and low profile.<ref name="Davis" />