This is a 510 thread 400mAh vaping battery with variable voltage and a convenient preheating function. The battery uses a convenient twist feature at the bottom to adjust the voltage between 2.0V and 4.0V. You can activate the preheating feature by pressing the button 2 times. You can also lock and unlock the battery button by clicking the button 5 times within 2 seconds. The battery includes a screw on USB charger.