2x Pack - Compatible APC SMART-UPS SC 420VA SC420 Battery - Replacement UB1290 Universal Sealed Lead Acid Battery (12V, 9Ah, 9000mAh, F1 Terminal, AGM, SLA) - Includes 4 F1 to F2 Terminal
Amazon.com: Replacement for APC Smart-UPS SC 420VA SC420 Battery - Replacement UB1280 Universal Sealed Lead Acid Battery (12V, 8Ah, 8000mAh, F1 Terminal, AGM, SLA) - Includes Two F1 to F2 Terminal Adapters :
APC UPS Battery Swap - Smart SC 420 - YouTube
Best Buy: APC Smart-UPS SC 420VA Battery Back-Up System Grey SC420