Choice of 3 Red Fuel - Fuel Packs for Back-up Power for Smartphones, MP3 players & Tablets Option 1 - SL3 series 2600 mAh 2600mAh Lithium Ion Battery Option 2 - SL4 series 4200 mAH 4200mAh Lithium Ion Battery Option 3 - SL5 series 10000 mAh 10000mAh High Capacity Lithium Ion Battery See below for full descriptions. Select option from dropdown menu