Panasonic KX-TG5561 Cordless Phone Battery Ni-MH, 3.6 Volt, 830 mAh - Ultra Hi-Capacity - Replacement for PANASONIC HHR-P104, Sony MDR-RR800/900 Series Rechargeable Battery Replacement Battery for PANASONIC HHR-P104, Sony MDR-RR800/900 Series - Ni-MH, 3.6 Volt, 830 mAh. Compatible with your OEM battery. Made with high quality cells.