【 5557 2P Plug Battery 】: This high-capacity replacement Li ion battery is compatible with ILIFE A4S robot. Compatible with A4、A4s、A4S pro、A6、A7、A9、A10、V3x. Compatible with V7、V7s、V7s Pro 、V7s Plus、V7 PRO、W400、W400s、px b020. Suitable for W450 sweeping robot series PX-B020 4INR19/66 M26-4S1P-1. Safety performance: Built in protection circuit effectively protects rechargeable batteries from overcharging, overdischarging, and short circuits.