The 8 - Cell 58Whr Li - Ion Laptop Battery is designed specifically for IBM ThinkPad X40 and X41 notebooks. With a capacity of 4000 mAh and an output voltage of 14.4 V DC, this rechargeable battery ensures reliable power for your laptop, allowing you to work efficiently without interruptions. Its proprietary battery size and lithium - ion chemistry provide optimal performance and longevity, making it an essential accessory for your laptop. Whether at home or on the go, this battery will keep your device charged and ready for use.