Tempered Glass and serve for that and protect from scratches and brake. There are some thin and cheap Tempered Glass with curved 2.5D and 3D edges and you will not notice... at least to protect screen in first 12 months while iPhone is new, later you could remove if annoy you. I even tried to install on back side of my iPhone SE but than I lost completely feeling of iPhone and I removed immediately from back side. I like to touch with hand nice iPhone surface not Screen protector, but on screen you can't notice at all and it's is necessary. 0.20mm is I thinnest I think. My precious is too significant to stay exposed without screen protector. 🙂