Compatibility: Replacement battery (1-pack), compatible with E35, E25, E28, and C28. Reliable Battery Performance: Made with high-quality battery cells, offering top-tier safety features against short circuiting, overcharging, over-discharging, and overheating. Easy Installation: Simply remove your machine's battery cover, unlatch to take out the old battery, then insert the new one with the sticker side up. Genuine Anker eufy Accessory: To protect your robot vacuum and extend its lifespan, we recommend using genuine replacement parts. Third-party alternatives may not be compatible and may affect performance.