This is a 12 cell Li-Ion rechargeable battery designed to work in WinBook WJ 4000 series laptop and notebook computers. This battery offers up to 60% more run time then the original NiMH battery and ships fully charged, tested and ready to work. This laptop battery is built with the highest quality standards, safety features and has a 1 year. Our batteries and accessories are guaranteed to meet or exceed the original equipment manufacturers specifications. Many are assembled right here in the USA by highly skilled American workers.