Acase 3500 mAh Extended-Life Battery with Cover for HTC Droid Eris (Black) Made from the highest quality Lithium Ion cells. Comes with a black case featuring Acase soft touch coating. Keeps your phone charged and ready to go, even with heavy phone and data usage Capacity: 3500mAh In order to obtain the full capacity of your Acase battery, we highly recommend that you leave the battery/your phone on the charger for an additional 2-3 hours after the charging indicator turns green or the battery status show Adds only 3-4mm to your device