Compatible with Philips Sonicare HX7351 HX7361 HX7500 HX1525 HX1520 HX2520 HX9552 HX9500 HX9882. Please, notice that to replace the battery it is necessary to disassemble the Toothbrush. All Toothbrushes require soldering to install battery. If You are not sure that You can disassemble the Toothbrush and install the battery correctly, we recommend to ask a specialist for help. The battery size is 1.65 x 0.67Inch (42x17mm), before making the purchase, please make sure the size of your old battery is the same. How to determine polarity correctly: The positive contact + is where the notch on the battery is, where there's no notch, it is minus -