A Single Tank Adapter (STA) allows for easy transitioning between a single tank setup and a doubles setup. The tank straps for a single tank setup go through the STA instead of through the backplate, allowing the switch to occur by simply removing the STA.

Some folks prefer to dive with an STA, even when not switching between setups, because it adds extra space between the tank and the diver's head. The use of an STA also reduces the amount of lead required by a diver to achieve neutral buoyancy.

Note: An STA is not required for single tank setup, nor does it add extra stability to the tank; it adds space, convenience, and weight only.