I've taken the plastic screen protector out of every Otterbox Defender that I've ever used. Just don't like the feel of them. I'll use them with no screen protector or a glass protector when I can. If your careful and work slowly, the plastic screen protector will come off undamaged and can be reapplied. Just push firmly along the edge from the outside inwards and it will come off with the sticky adhesive, sometimes that adhesive will remain on the case but as you work the plastic protector off just tap it back to the adhesive and lift again peeling it away with your fingers.
I currently have a Luvvitt glass on mine, I have another one I may try since this one has a slight halo in a couple of areas. With it and the Defender you end up with a small gap along the sides, bottom and around the home button. I expect that it would be similar with other brand glass protectors. It fits fine in the Defender. Luvvitt doesn't provide specs on thickness of their glass but it seems to be the same as others I've used and if I were to guess I'd say it's about .30mm, not the thickest I've ever used but not super thin either, just a normal glass protector.
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