Stay unplugged longer. Get twice the capacity of the 4-cell system battery and up to 7.9 hours of battery life on select systems. The ThinkPad X60 Series 8 Cell High Capacity Battery has an extended section on the back edge and fits in the standard ThinkPad X60 Series system battery slot. It can remain in the system when the system is connected to the ThinkPad X6 UltraBase.