RND Extended High Capacity Lithium-Ion Battery (35H00142-09M) + Back Cover for HTC ThunderBolt 4G Perfect High Capacity battery made specifically for your HTC ThunderBolt 4G Smart Phone Designed to extend the battery life of your phone at an affordable price. Comes with a black replacement door. RND Power Solutions products are quality batteries offered at a great value. Capacity: 2200mAh