This 10.8V, 9-cell Li-Ion high capacity battery provides up to one-third more capacity than the standard system battery. This high capacity battery has an extended area on the back edge and fits into the standard ThinkPad T40/R50 system battery slot. The dream of an all-day computing experience becomes a reality (up to 8 hours on select systems) when you combine the ThinkPad T40/R50 Series High Capacity Li-Ion Battery with the optional ThinkPad Ultrabay Slim Li Polymer Battery.