Boostcase BCH1900B-YC2 Hybrid Snap-On Case and Detachable Extended Battery - Retail Packaging - Black/Yellow Hybrid two-piece case/battery design, only attach the extra battery when you need it Half-ounce ultra slim snap-on case for iPhone 4 and 4S (Choose from up to 9 different colors) Two ounce 1900mAh detachable extended battery doubles battery life for iPhone 4 and 4S (Available in Matte Black or Glossy White finish) Fully functional battery with Battery Level indication, Power On/Off and Simultaneous Sync/Charge CES Innovations Award Winning Design and Made for iPhone certified