The EGO 21″ Self-Propelled mower is equipped with Peak Power™ Technology. Peak Power™ combines the power of any 2 EGO batteries for longer run time and efficient power draw. The push start button provides a quick and easy start, while the self-propel speed control allows you to power through tough terrain at your personal preference. Compatible with all EGO POWER+ ARC Lithium™ batteries (Sold Seperately) to deliver Power Beyond Belief™.