The APC SMART-UPS POWERSTACK 450VA is a UPS system that requires a 6V 7Ah AGM replacement battery. The compatible Universal Power Group replacement is the UPG UB670 6V 7AH F1 AGM Battery (UB670), a 6V 7Ah AGM sealed lead-acid battery. This battery delivers up to 42 watts of standby power. It weighs 2.43 lb, uses F1 terminals, measures 5.94 L x 3.7 H in, and has right polarity. This is a direct drop-in replacement for the APC SMART-UPS POWERSTACK 450VA requiring no modification to the device.