A mechanical mod has no wires. You have the battery holder, a switch, and 510 connector. A vv, or variable voltage is regulated by a circuit board. It keeps your output to a specified voltage until the battery drops to the point it can't keep up. There is built in protection with these types and won't fire if you're atty has a short. A mechanical, no protection. You must learn ohms law, battery safety and test your atty for shorts before putting it on your mod. Hope this helps a little.