2-Pack 3.6V 800mAh Extended Replacement Battery for Plantronics 63421-01 , CT11 , CT12 & More Accessory Power truCELL Brand, Non-OEM Equivalent; Replaces Plantronics 63421-01 Designed to meet or exceed OEM specifications Chemistry: Ni-MH, Capacity: 800 mAh, Voltage: 3.6 Constructed from premium nickel-metal hydride cells for quality and performance Guaranteed Quality ***3 Year Manufacturer's Warranty***