2 Pack Sony BP-HP550-11 Battery - Replacement for Sony BP-HP550-11 Headphone Battery Replacement Sony BP-HP550-11 Battery 2.4V 700mAh Battery Type:Ni-MH 1 Year Replacement Warranty High quality, high capacity, light weight rechargeable battery Compatible with Sony MDR-840, Sony MDR-850RK, Sony MDR-925, Sony MDR-970RK, Sony MDR-RF810, Sony MDR-840RJ, Sony MDR-860, Sony MDR-925RK, Sony MDR-RF4000, Sony MDR-810K, Sony MDR-850, Sony MDR-860RK, Sony MDR-970, Sony MDR-4000RK, Sony MDR-RF4000K, Sony MDR-RF810RK, Sony MDR-RF840, Sony MDR-RF840RK, Sony MDR-RF850, Sony MDR-RF850RK, Sony MDR-RF860, Sony MDR-RF860RK, Sony MDR-RF925, Sony MDR-RF925RK, Sony MDR-RF970, Sony MDR-RF970RK. Not Compatible with MDR-RF970R