Professional manufacturers. Many years of production experience. Tested under strict quality control standards with professional machines 3 times before shipping. Over-Charging, Over-Discharging, Over-Heating and Short-Circuiting Protection. Speed up your phone.Instruction/Manual NOT included, but there are many installation tutorials videos on YouTube to reference. Easy to replace,most people should be able to do it. Replace your old battery perfectly.All batteries are tested before shipment, your phone will work as great as when you first got the device.Please contact us when you have any questions, whether pre-sales or after-sales. Value Plus products have a very good after-sales service. Please choose us with confidence.Our battery may sent out with little or no power, please make full charged first if phone can not turn on.It is recommended to fully drain and fully charge the battery especially during the first 3 charging and discharging cycles, doing so may greatly improve the overall life of the battery.