Need a battery for HP Laptops/Notebooks with the following model numbers: Probook 4320S, 4420S, 4520S, 4720S? BTI has you covered with our premium 6 cell LiIon battery. This product has been engineered to meet or exceed the original manufacturer's specifications and replaces the original HP part numbers PH06, BQ350AA#ABA, 587706-541, 593572-001. All BTI batteries are manufactured and tested under our stringent quality standards and come with an industry leading 18 month manufacturer's warranty. BTI... True to the original.