Auto-eGo FS520 Series 1,Auto Battery for FS510/eGo series. 2,650mAh or 300mAh for choice. 3,Available for all types of 510/eGo cartomizers and tank systems. 4,Easy to carry with key-ring. 5,Simple pocket-ecig design. Products details ***General Introdution: FS520 uses the bigger type auto batteries of 650mAh or 300mAh for choice. There is no key-press as manual battery. You can smoke the big E-cig like the regular small e-cig, freely and favorably. FS520's screw/nut is fully compatible with 510/eGo series' components. They use the same cartomizer, FS-T3, FS-T4, FS-T5, FS-T6, etc. Their USB charger/adapters are the same too. So we can call it Auto-eGo. *** Main structure: * FS520 with cartomizer: FS520 Battery + Cartomizer + Shell * FS520 with tank system: FS520 Battery + Convertor + Tank * FS520 with T-atomizer: FS520 Battery + Convertor + T-atomizer + Mouthpiece * FS520 Battery: 300mAh or 650mAh for choice. Input: 4.2V, 60/50Hz Battery head with key-ring. * Cartomizers: FS510/eGo cartomizer (no need convertor); T-atomizer, C-atomizer, FS-Tank systems like FS-T1, FS-T2, FS-T3, FS-T4, FS-T5, etc.(with convertor) * Charger: Wireless USB Charger (no need convertor, designed especially for FS520 battery) Regular eGo USB charger + Convertor. * FS520 with tank system. (FS-T4 in the picture) * FS520 with T-atomizer. * FS520 wireless USB charger.