Replacement battery for Galaxy S3

Well, I saw these, and was wondering if you ever tried any, do you suggest them or if you have any idea?

http://www.ebay.com/itm/3800-Extended-Battery-Black-Back-Cover-Skin-Case-for-Samsung-Galaxy-S3-III-i9300-/121041525945?pt=PDA_Accessories&hash=item1c2ea31cb9
http://www.ebay.com/itm/6000mAh-Extended-Battery-Back-Case-Cover-For-Samsung-i9300-Galaxy-S-III-3-S3-/181000054378?pt=AU_MobilePhoneAccessories&hash=item2a2471a66a

Are they worth it?
Answer #1
The batteries are not authentic and not from samsung. I wouldn’t recommend it.
Answer #2
Yes, they are worth it, bot sellers have excellent feedback scores, which they wouldn’t have if they sold junk. “authentic” means nothing. these could be much better than “authentic” packs, as “authentic” packs are made as cheap as possible, and made to break down just after the warranty period. these packs could have quality cells made in japan, whereas the “authentic” packs could have cells made in a country that makes them cheaper!. this IS the way it works for electronics.
Answer #3
And could the battery anyhow damage my device or it got nothing to do with it?
Answer #4
If there’s more mAh in the battery, it will be bigger than the original one, I suggest you get a genuine Samsung battery
Answer #5
If there's more mAh in the battery, it will be bigger than the original one, not necessarily, it may just have better batteries, and if it is bigger, as long as it works properly, there's no problem. I suggest you get a genuine Samsung battery
for the good that will do, he can just write samsung on the battery pack.
Answer #6
If there's more mAh in the battery, it will be bigger than the original one, I suggest you get a genuine Samsung battery
That’s the whole idea – it should also last longer as well, that’s why the higher MAh (and a replacement battery cover) I have a couple of them for my GT-I9305 (I carry a spare but never really need it, unlike a standard Samsung one).