1. The coil is made of 100% pure copper enameled wire, the copper wires are evenly arranged, and there will be no problems such as excessive temperature rise, torque decay, and louder noise after long-term operation. 2. The circuit board is welded by a fully automatic welding machine, which is more evenly distributed, stronger and more beautiful than the traditional process. 3. The of the rotor is coated with epoxy resin to prevent the of the rotor from adsorbing burrs. The magnetic field of the motor is more stable, the torque is larger than similar products, the motor runs smoother, more stable, lower noise, and longer service life. 4. The PCB board is strengthened in the motor, and stator technology is used to that the stator teeth of the motor are ground uniformly and smoothly. The inner hole is high in precision, and the rotation speed is stable and accurate during work without losing steps. 5. Stable speed and low noise. The motor has high overall stability, uniform speed and low noise after Kossel, Prusa l3, Ultmaker, corey and other motors. Number of phases: 2 Rotor inertia: 57g.cm Step angle: 0.9degree 5% Weight: 0.28kg Rated voltage: 4.3V Insulation class: B Rated current: 1.3A Resistance (20degree ): 2.2x(115%)ohm Ambient temperature: -24Celsius-+80Celsius Inductance: 5.7X(120%) Relative humidity: 90%MAX Life: 5000 hours Colour:black Material:metal Size:42 x 38mm Package Contents: 1 x 42 Stepper Motor Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.