Auto-draw, adjustable voltage. Cleaning Tip: It's always a good idea to "burn off" any concentrate left on the coil after your session, to avoid excessive build-up that can hinder the performance of the terp pen. The coil can also be cleaned with a Q-tip lightly-dipped in isopropyl alcohol. Ask a budtender familiar with concentrates to explain the burn-off process, if you are unfamiliar.