Variable voltage: 3.5V, 3.7V, 3.9V, 4.2V (3 times click the fire button to switch voltage, 4 LED's on the side, green light will appear for 2 sceonds indicating which voltage you have selected)
510 threading connection with spring-loaded brass center pin
Side mounted fire button
Houses single 18350/18500/18650 battery (battery sold separately)