This is an APC external battery pack designed to extend the runtime of an APC Smart-UPS SRT unit in the 5kVA or 6kVA capacity range. A UPS's internal battery typically only bridges a relatively short outage at full load; adding this extended battery pack lets the same SRT UPS keep connected servers, network gear or other critical equipment running for longer during a power cut, which matters for data centres and server rooms — and in South Africa, specifically for riding out longer load-shedding stages. It's a battery expansion accessory rather than a standalone UPS, and requires an existing compatible APC SRT 5/6kVA unit to connect to.