Specifications: - Battery type: Li-ion - Voltage: 11.1 also compatible with 10.8v - Capacity: 4400 mAH Compatible Models: HP ProBook 4320, ProBook 4425s, ProBook 4320t ,Compaq 320, HP 420, ProBook 4325s, Compaq 321, HP 425, ProBook 4326s, Compaq 325, Compaq 421, ProBook 4320s, ProBook 4520, Compaq 425, ProBook 4321, ProBook 4520s, Compaq 620, ProBook 4321s, ProBook 4525s, Compaq 621, HP 620, ProBook 4420s, Compaq 326, HP 625, ProBook 4421s, Compaq 420, Compatible part numbers: HSTNN-IB1A, HSTNN-CB1A, HSTNN-DB1A, HSTNN-CBOX, HSTNN-LB1A, HSTNN-Q78C, HSTNN-Q78C-3, 587706-761, HSTNN-Q78C-4, HSTNN-Q81C 587706-761, 587706-751, 593572-001, BQ350AA, HSTNN-CB1A What's in the box Laptop Battery