BATT-CS50 - Li-Ion, 3.7 Volt, 230 mAh, Ultra Hi-Capacity Battery - Replacement Battery for Plantronics 64327-01,65358-01 Wireless Headset Batteries Replacement Battery for Plantronics 64327-01,65358-01 Wireless Headset - Li-ion, 3.7 Volt, 230 mAh. 100% compatible with your OEM battery - 3 year warranty. Made with high quality Japanese cells. Synergy Digital is a Registered Trademark