The AP 300 S is a high capacity battery that will power any tool within the STIHL PRO Cordless system. With an energy capacity of 281 Watt-hours (which relates to run time), this battery offers an impressive 25% increase in capacity compared to the AP 300, and with an Amp-hour capacity of 7.8, this battery will consistantly power PRO Cordless tools for longer. The four LED lights let you know how much charge is left within the battery.