Fully CompatiblityHisewen HK-OS4 replacement Battery Compatible with Harman Kardon Onyx Studio, Onyx Studio 2, Onyx Studio 3, Onyx Studio 4. Battery Specification High Capacity: 3500mAh, Voltage: 3.7V. Rechargeable Li-ion battery. Screwdriver ToolHarman kardon onyx studio 4 battery comes with screwdriver tool, you can replace the old battery easily. Hisewen is committed to providing thoughtful and attentive service to every customer. Multiple ProtectionHarman kardon replacement battery built in overcurrent, overcharge, overvoltage, overheating, shortcircuit protections, ensure battery safety. Package List1 Pack HK-OS4 battery, 1 set screwdriver tool, 30 days refund and 12 months warranty. If you have any problems, please feel free to contact us!