Before Installation Notes1. Tips 1: Test before installationWhen testing, do not remove any protective film or tags. Please pay attention to the problem of static electricity.Before attempting any repair, be sure to ground yourself is an ESD (electro static discharge) strap. This will prevent static electricity from damaging the electronic components within the phone.Ensure you wear eye protection and use caution not to cut your finger with the glass splinters.2. Tips 2: Simulates testingScreen replacement is very fragile product. We strongly suggest test before installation. Please simulates testing, which means mobile phone apart, (motherboard + LCD or screen) connected audio cable and new replacement, power on, test finished. If test OK, please install it. If it can not show, please contact us at the very first time. And please do not force it to be installed in mobile phone. We will not be responsible once the screen is installed.3. Tips 3: Do not over-bend cablePlease make sure LCD cable Do not over-bend. Over 90 degrees bent will cause black display.About the product1. Replacement LCD display + touch screen digitizer assembly (OLED material) for for Samsung for Galaxy J4 SM-J400.2. Replace the old, broken, cracked, damaged one.3. Make your device look more refreshing than ever.4. Completely fit and work.5. Each item has been checked and in good condition before shipping.6. Professional installation is highly recommended. We will not be responsible once the screen is installed.