The Dynavap is a portable dry-herb vaporizer, most often powered by a butane torch lighter and Dynavap's clicking cap. They don't run on electricity, and the simple materials/lack of electronics makes them highly durable and reliable.
To use it, simply fill with material, put the cap on, and spin it over your flame. When the Dynavap is at the proper temp, the cap's bi-metal disc indicator will click, letting you know to stop heating and begin hitting. When it's cooled down it will click again, resetting the discs and letting you know it's ready for another heat-up.