HQRP Battery 2-Pack for Sennheiser Set840-S Set840-TV Set900 Set830 Set830-S Set830-TV RR840 RR840-S RS4200 Headphones Receiver + Coaster HQRP&reg; Two Rechargeable Batteries Replacement plus HQRP&reg; Coaster; Battery Voltage: 3.6V; Capacity: 140 mAh; Li-Pol; 200 Days warranty!