This is an APC extended battery pack accessory compatible with APC's 8kVA and 10kVA UPS models, sold to extend backup runtime beyond what the UPS's own internal battery provides. Larger UPS units like these are typically deployed to protect server rooms, comms cabinets or small data centres, and adding one or more extended battery modules lets an organisation ride out a longer power outage or extended load-shedding stage before equipment needs to be shut down. The listing doesn't specify the exact Ah/VAh capacity or which specific 8kVA/10kVA model numbers it's compatible with, so buyers should confirm exact model compatibility against APC's documentation before purchase.