SDEN4 Ni-MH Battery - Rechargeable Ultra High Capacity (7.2V 2100 mAh) - Replacement for Nikon EN-4 Battery for D1, D1H & D1X Digital Cameras Replacement battery for the Nikon EN-4, Nickel Metal Hydrate (NI-MH) 7.2V (2100mAh) 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark