Below is an excerpt from the Mophie Website. Note that they have an option for iPhone 5 users too!
Need even more battery power for your iPhone? The mophie juice pack plus® has our largest battery which extends the battery life of your iPhone for hours! The juice pack plus also provides a comfortable ergonomic design with the complete protection of a dual-injected hard shell case with protective rubberized band.
Since it is designed to more than double the time you have to Rock, Talk, Surf and Send with your iPhone , the mophie juice pack plus is the ultimate iPhone 4/4S battery case for travel or business. The simple toggle switch allows for standby and charging mode so you only have to use the juice pack plus battery when you need it!
More than double the battery life.
Take full advantage of everything your iPhone has to offer, such as Web browsing, downloading apps, sending emails, or watching video without worrying about always having to recharge.
Featuring Apple’s coveted “Works with iPhone” certification, this innovative smart battery case adds up to an additional 8 hours of talk time (up to 16 on 2G) or Web browsing to your iPhone 4/4S
