We’ve introduced some iPhone 4 battery cases, but if you want a slimmer case, the Third Rail iPhone 4 case with detachable external battery may be more suitable for you.
The iPhone 4 case kit is called Third Rail System that consists of two parts, including an ultra slim iPhone 4 to protect your iPhone 4 from scratches and bumps, and a portable rechargeable battery with 1250mAh capacity that measures 3.29 x 1.83 x 0.27 inches and weights 1.4 oz. As we can see from the images, the back up battery hasn’t been integrated into the case. This means the battery doesn’t always add some bulks to the iPhone 4 case. As necessary, the external battery can expand the use time of your iPhone 4.
Third Rail iPhone 4 case with detachable external battery us priced at $89.99 USD. If you’re interested, jump to Third Rail Mobility for more details. Additionally, if you need more options, you might like to check XPAL battery case, Incase Snap battery case, and more via “iPhone 4 case” tag.