Compatible with - HP/Compaq Mobile Thin Client: 4320t. - HP/Compaq Notebook PC: 320, 321, 420, 421, 620, 621. - HP/Compaq ProBook: 4320S, 4321S, 4325S, 4326S, 4420S, 4421S, 4425S, 4520S, 4525S.