Thank you for choosing us. Please take note of the following key points to ensure a smooth screen replacement process: 1. Confirm Compatibility: Before purchasing, verify the exact model of your device. This product is specifically designed for Samsung Galaxy S21 5G screen replacement (model numbers : SM-G990 SM-G991 SM-G991B SM-G991U SM-G991W) and is not compatible with other models. If you have any doubts, please consult official channels or check the model number in your phone settings. 2. Prepare Necessary Tools: Ensure you have specialized disassembly tools, such as precision screwdrivers, suction cups, and spudgers, to safely and efficiently replace the Samsung Galaxy S21 4G LCD display. 3. Power Off Completely: Before starting disassembly, fully shut down your phone and, if possible, remove the battery or disconnect the power to prevent electrostatic damage to internal components. 4. Handle with Care: When removing the old screen, proceed gently and avoid applying excessive force to prevent damage to the screen connectors or the phone body. 5. Test Functionality First: Before fully reassembling, connect the new screen assembly and power on your phone to test all functions—including touch sensitivity, display quality, front and rear cameras, sensors, etc.—to ensure everything is working properly. 6. Consider Professional Installation: If you are not confident in performing the replacement yourself, it is recommended to seek professional repair services to avoid more serious device damage or safety hazards due to improper handling. Following these guidelines will help minimize potential issues during the screen replacement process, leaving your phone refreshed and fully functional.