he Wulf Duo by Wulf Mods consists of a mouthpiece and cartomizer which is recessed into the mod. The housing is made from durable material and made to take lots of wear and tear. You can choose from four different voltage settings to customize the experience to your liking. The voltage settings are 3.4, 3.6, 3.8, and 4.0V. Different LED colors serve the purpose of letting you know which voltage setting is being used. Everything is accomplished with a simple one-button operation.