The Voopoo Drag Mini is an awesome internal battery device.
It offers you the fantastic functionality of the Gene Fit chip, with the simplicity of built in batteries. The Drag Mini is fitted with a 4400 mAh battery inside with a maximum output of 117 watts which still allows for the use of most tanks. This device is noticeably smaller than its big brother, the Voopoo Drag 2, and is also substantially lighter too.
As mentioned, the Drag Mini uses a Gene Fit chip. This chip boasts the same insanely fast firing speeds that the original drag offered while introducing a fire/dust proof barrier. The Gene chip also has a 'fit' mode which has three pre-set settings. One which optimize battery life, another to optimize flavor, and a third to optimize cloud production.
Voopoo recommends using their U-Force tanks to get the best experience out of the 'fit' mode.
Overall the Drag Mini is a great option for someone looking to avoid using external batteries.