Battery for headsets. Compatible replacement battery, not an original battery from the manufacturer! Refer to the device and battery numbers listed to select the right battery for your device! Replacement battery suitable for: Sony: MDR-RF4000, MDR-RF4000K, MDR-RF810, MDR-RF810RK, MDR-RF840, MDR-RF840RK, MDR-RF850, MDR-RF850RK, MDR-RF860, MDR-RF860RK, MDR-RF925, MDR-RF925RK, MDR-RF970, MDR-RF970RK Identical to the following batteries: Sony: BP-HP550-11 https://elecena.pl/product/18447785/30082-battery-for-sony-mdr-rf4000-nimh-700-mah 2021-05-13 https://elecena.pl/product/18447785/30082-battery-for-sony-mdr-rf4000-nimh-700-mah 2022-05-24