The HP HK04054XL battery is a lithium-ion replacement for a laptop that uses this identified HP battery model. The listing also identifies it as model HK04XL, HP part number L82391-006, and reference HK04054XL-PL.
Its 4-cell design has a rated capacity of 54 Wh (3.54 Ah) at 7.7 V. These figures describe its stored energy, charge capacity and operating voltage, helping you check the battery specifications against the one being replaced.