HP RU03XL is a lithium-ion replacement battery for a notebook that uses this model. The distributor also identifies it by HP part number L12791-852, helping distinguish it from other HP batteries.
Its three-cell construction provides a stated capacity of 48 Wh. The listing also specifies a charge capacity of 4.21 Ah; these figures describe the RU03XL’s energy storage.
This is a battery component, not a power adapter or external charger.