STIHL offers three different battery systems for its products: AS, AK, and AP. It's when you get to the AK and AP battery systems that things become a bit more challenging to distinguish. The difference is that AK batteries are meant for models made more for your average homeowner needing to handle tools like this, and AP batteries — short for ALLPRO — are the ones designed for professionals. While they serve similar products, AK and AP batteries aren't interchangeable. For instance, AK batteries will work on STIHL RMA lawnmowers with 348, 448, and 460 model numbers, but AP batteries are needed for RMA models 453, 510, 756, 765, and 7.