I just placed the order, haven't tried it out yet but the items get high user ratings. All of the extended batteries come with a new back for the phone. The really difficult thing is to find a protective case that will fit the new dimensions of the phone with extended battery, this makes it roughly twice as thick. I found one and it is only 5 bucks on amazon.
QCell Samsung Galaxy SIII X-Life NFC enabled 4200mAh Extended Battery + Blue Back Cover (Compatible with Samsung Galaxy S III GT-i9300, AT&T Samsung Galaxy S3 Samsung i747, Verizon Samsung Galaxy S3 Samsung i535, T-mobile Samsung Galaxy S3 Samsung T999, U.S. Cellular Samsung Galaxy S3 R530, and Sprint Samsung Galaxy S3 Samsung L710) **WITH NFC FOR S BEAM & GOOGLE WALLET SUPPORT** - QCell
22bucks
Hyperion Samsung Galaxy S III Extended Battery HoneyComb TPU Case Black (Hyperion Retail Packaging) **Compatible with ALL Hyperion, Qcell, Onite, Anker, and most Generic Galaxy S3 Extended Battery Models**
5 bucks
I'll get back with a review once I know how it all works.
Vickie