It's such a tight fit that the phone is prone to pop out of it and if you drop it face down then it might not offer any protection. My case still stuck out over the glass a little bit but if it had been dropped it probably would have just fallen out of the case and the glass would still hit concrete - also what little was left sticking out would have made the smallest pebble hit the screen as well. I got the case you have free with the phone but couldn't keep using it because of those two things;
- That it didn't offer appropriate drop protection (which was awesome with that particular case prior.
- That it might just come out of the case too easily even if it did offer appropriate protection.
I went to a guy that had a pretty sizable mobile phone accessory stand in a shopping mall and he had a case for the normal gs2 battery that happens to fit the extendable battery. I'd go and ask people until you find someone that states having one that works and then trying it on. The first one I tried fit, but it was clear and I wanted black. He had the same one in black but when I tried it on at the shop it didn't line up properly like the clear one regardless of being the same case in a different colour; so that's my advise, is to find someone that will let you try a case at the shop, but be up front that you have the extendable battery. If they don't know what you're talking about when you tell them that, and that your phone is bigger as a result, then go elsewhere until you find something appropriate from someone who knows what they're getting into when they try it on your phone before buying.