Buy with confidence, I bought it and it came in the same box it came in when I worked for the company, meaning it is AUTHENTIC.

Tip for the change: The back cover requires A LOT of heat with a hairdryer, heat it until it can't be touched with your hand without fear. When opening the cover, be careful not to cut the ribbon cables in the middle of the back, and avoid hitting the cameras with the tool. Swipe a credit card around the edges, not too deep, at the edge. Also, be careful with the earpiece, insert a screwdriver inside the notch and lift it from below because it easily separates into two parts, and then you will hear buzzing during calls. Also, get an authentic adhesive specifically for this model to close it properly. Clean any remaining adhesive from the cover and the back of the phone for a perfect fit. Also, removing the battery is ********. Heat it up, but not too much, and insert the card from below, trying not to bend it. It's better to bend the old screen to remove it than the battery. Also, try not to damage the adhesive so that it sticks to the new screen.

CAUTION: After the change, your fingerprint will NOT work. It requires calibration, which can ONLY be done at authorized Samsung Service Centers. Whether they will do it for you (normally they don't charge, but they MIGHT format your device, so first backup your data) depends on the employee or the store.