The material is tempered glass ... but very very fine!
I still managed to streak the good of 1 cm in trying to hunt a bubble of a corner during installation!
Since I used the little piece of plastic provided for this purpose, I have a doubt about the effectiveness of the product in a more substantial impact.
In conclusion: to protect the screen from scratches ... just like the plastic film glued to the screen
Keep your 8, do not peel off the plastic film of your new S5 :-)
PS: protects the screen of a drill on the product photo => but on ...