The Fuse is a safety module for mechanical mods. It has a 5-amp limit, meaning that if you are vaping at 5 amps or higher, the fuse will introduce a safety cut-off. The Fuse is magnetic and is most effective when placed under your battery, with the "button" touching the bottom of the battery. Without The Fuse, a mechanical mod will not stop firing as long as the button is pressed. If left unattended, the mod can fire for minutes at a time, causing venting and excessive heat. The Fuse prevents that by breaking the circuit after a period of time. The Fuse will trip after 20 seconds at 5 amps, and the more amperage that is drawn from the battery, the shorter the amount of time it takes for The Fuse to trip. After The Fuse is tripped, it is re-usable after a brief period of time. The Fuse adds approximately 5mm to the length of your battery and will not affect vaping performance under normal use.