HQRP Battery compatible with Sennheiser RR820 / RR 820 / RR820S / RR 820 S / RR2500 / RR 2500 / HDR65 / HDR 65 / HDR80 / HDR 80 Headphones/Receiver plus Coaster HQRP&reg; Rechargeable Battery plus HQRP&reg; Coaster; Battery Voltage: 2.4V; Capacity: 80 mAh; Ni-Mh; Compatible with Original Battery; 200 Days warranty! Hear to win with HQRP&reg; replacement battery!