Features and Specs: Driven by an 10 Watt, high-torque, Swiss made, Maxon precision motor. Fully American manufactured and assembled. Constructed of 6061-T6 aluminum, finished in Mil Spec Type II anodizing. American made Main Bearing 5 strokes in one machine, changeable on the fly Primary range of 5 volts – 14 volts (motor will start and run down to 3v) Lubricated for life No need for maintenance Uses RCA connection (**does not come with cord**) 2.5mm, 2.9mm, 3.4mm, 3.8mm, 4.2mm This isn’t just another pen with a spinning grip. You not only adjust needle protrusion with the Valhalla’s grip, but the stroke options allow you to choose your hit. Whatever you need to do: lining, packing, coloring, blending, shading, its all there at your fingertips, 5 strokes in 1. You never need to break down your setup to change the hit. Keep’er bagged. You simply twist the stroke ring in the center of the machine, on the fly, and you’re hitting exactly the way you want! Pen machines have a lot of benefits and reducing fatigue is one of them. The Valhalla also reduces vibration. Your body will thank you from your hands to your back. PS: It’s also the cleanest pen on the market with a high performance seal surrounding the plunger bar which resists flow in both direction. The Valhalla’s design also eliminates traditional dirt traps by being the first machine to use single rotation threads on the grip receiver and an absolute minimum of sharp corners or cavities. It’s the easiest to clean and the hardest for dirt to hide on.