Spigen’s GLAS.t adds a thin layer of tempered glass to protect your iPhone 4 or 4S screen protectors. Glass is three times harder than plastic and can survive an attack from scissors or box cutter. Glass will break into thousands of little pieces instead of sharp glass daggers. The $28 screen protector adds minimal thickness to the iPhone 4S and doesn’t affect its touchscreen function. It’s also three times hardier than plastic, and it’s three times tougher to break than plastic.”]
Source: https://gizmodo.com/protect-your-iphones-glass-display-with-more-glass-5880507