Southwestern Bell FF-4000 Cordless Phone Battery Ni-CD, 3.6 Volt, 900 mAh - Ultra Hi-Capacity - Replacement for Sony BP-T50 Rechargeable Battery Replacement Battery for Sony BP-T50 - Ni-CD, 3.6 Volt, 900 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark