This is the Tekin Pro4 HD 1850kV 4-Pole Brushless Motor. Tekin's Pro4 HD Motor raises the bar in 4wd short course, with the torque and power needed to level the competition. With kV ranges to accommodate 2S, 3S and 4S applications, 1/10 4WD Short Course has never been exposed to this much power! The Pro4 HD's longer 550 can and 4 pole design delivers the off the charts performance gains you need to move your truck to the front of the pack. Features: Designed to be paired with the RX8 Electronic Speed Control 4 Pole 12 Slot Hi-torque 550 Motor Design CNC Machined 6061 T6 Billet Aluminum Heatsink Can Neodymium Sintered Magnets Rebuildable Design High Purity Copper Windings Maximizes Efficiency Precision Engineered for Maximum Energy Conversion Dual-Plug Sensor Wire Harness for use with all sensored systems High RPM ABEC5 Oversized Bearings Specifications: Turns: 2Y Voltage: 2S - 7.4V / 4S - 14.8V kV: 1850 Rotor: 18.5mm Weight: 7.8oz / 221g Shaft Dimensions: .60x.196" / 15.3x5mm Motor Diameter: 1.4" / 35.8mm Motor Length: 2.5" / 62.5mm Bearing Dimensions: Front: 5x14x5mm / Rear: 5x11x5