AT-T/Lucent 4051 Cordless Phone Battery Ni-CD, 3.6 Volt, 400 mAh - Ultra Hi-Capacity - Replacement for Rechargeable Battery Replacement Battery for Rechargeable - Ni-CD, 3.6 Volt, 400 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark