2x Pack - Sony MDR-RF920RK Battery - Replacement for Sony BP-HP550 Headphone Battery (700mAh, 1.2V, NI-MH) Replacement Sony MDR-RF920RK Battery Replacement for Sony BP-HP550 Headphone Batteries Quantity: 2, Lifetime Warranty Capacity: 700mAh, Upstart Battery Brand On Sale for a Limited Time!