6 cell ultrabay battery?

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A rep told me that there are too kinds of ultrabay batteries. One is 3 cell, and the other is 6 cell. But I only find one kind of ultrabay battery on Lenovo's web, and I believe its the 3 cell version. Does anyone know anything about the 6 cell battery? Like what's the price, and weight, or things like that. Or just let me know if it doesn't exist.

My 4 cell battery can do over 2 hours, I believe, so if there is a 6 cell ultrabay battery, my machine may be able to work for over 5.5 hours without someting sticks out of it. That will be great, and I will sell my 7 cell for a 6 cell ultrabay. Thanks!