The STIHL AP battery adapter is required to transfer power from your STIHL AP-System battery or an AR backpack battery to a STIHL power tool with a battery slot. This also makes it possible to carry the battery on your body, reducing the tool weight. To do so, insert the adapter into the battery slot instead of the battery and connect it to the corresponding battery using the connecting cable. For this, you can use the AP adapter together with an AP holster with connecting cable, with the STIHL AR batteries.