There are a few ways to tell if a TF card is fake. One way is to check the capacity of the card. A genuine TF card will have a capacity of 16GB, 32GB, 64GB, or 128GB. Another way to tell if a TF card is fake is to check the speed class of the card. A genuine TF card will have a speed class of Class 10. Finally, you can check the warranty period of the card. A genuine TF card will have a minimum warranty period of 5 years.