You'll often see tempered glass screen protectors with a "hardness" indication somewhere on the package, usually "9H". This refers to Mohs Hardness Scale of Minerals, which ranges on a scale of 1 to 10. Regular glass is generally a 5 and a diamond is at 10. This hardness indicates the ability of minerals to scratch each other's surfaces. Glass can scratch anything below a 5, yet glass can be scratched by anything above a 5. By claiming that tempered glass has a hardness of 9H, you'd have to have a diamond in your pocket to test it. The fact is, we've tested a lot of tempered glass screen protectors out there and have yet to find one that tests better than a 6 or a 7.