new at- ace comes with three interchangeable lower blades adapts to your stride designed with speed iq™ self-propelled technology to digitally sense and adapt speed to your stride speed 10 ego self propelled cutting torque self propelled 21 ego ego™ power+ 56 volt 21" select cut xp self-propelled mower with speed iq includes 12 amp lithium-ion battery and charger selection and set self-propel mode in real time select cut multi-blade system delivers customizable cutting performance with three interchangeable lower blades ego cut athenssl digital display allows you to monitor battery mode in real time cuts up to 90 min on a charge ego