This is a 15W generator with copper windings designed specifically for wind turbines. Most DC motors are designed to spin at an RPM as high as possible, which means they can only generate power at a high RPM. Since this is a wind generator, we have designed the windings to start producing 12 volts at 1020 RPM. FEATURES Specifically designed for wind turbines: Optimized for wind turbine speeds (it requires significantly lower RPMs to generate power than most motors/generators) Shaft has a flat spot for attaching a set screw Includes two 3/16? spade terminals and blocking diode for power connection Be sure to check out our Gridless Revolution micro wind turbine hubs and blades! SPECIFICATIONS: Output: 12+ Volts DC @ 1020 RPM Shaft diameter: 0.196" (5mm) Shaft length: 0.370? (10mm) Generator diameter: 1.65? (42mm) Generator total length (including shaft): 3.560? (90mm) Generator weight: 10.8 oz Voltage output: 0-36VDC (36V at 3050 RPM) Maximum Generator Output: 15 watts