The ADA 100 AP adapter is for transfer power between a STIHL AP battery to an AP System STIHL tool with a battery compartment. It means you can carry the battery on your waits, reducing the overall weight of the power tool.
Simply insert the ADA 100 AP adapter into the battery compartment on your battery (instead of the battery) and connect it to the battery using the AR L connecting cable. It can be used with the AR 2000 L & AR 3000 L backpack batteries.